Bump shellcheck to 0.9.0

Fix everything it flagged.

cluster/gce/upgrade.sh

@@ -402,7 +402,7 @@ function do-node-upgrade() {
     if [[ "${set_instance_template_rc}" != 0 ]]; then
       echo "== FAILED to set-instance-template for ${group} to ${template_name} =="
       echo "${set_instance_template_out}"
-      return ${set_instance_template_rc}
+      return "${set_instance_template_rc}"
     fi
     instances=()
     while IFS='' read -r line; do instances+=("$line"); done < <(gcloud compute instance-groups managed list-instances "${group}" \
@@ -412,7 +412,7 @@ function do-node-upgrade() {
     if [[ "${list_instances_rc}" != 0 ]]; then
       echo "== FAILED to list instances in group ${group} =="
       echo "${instances[@]}"
-      return ${list_instances_rc}
+      return "${list_instances_rc}"
     fi
 
     process_count_left=${node_upgrade_parallelism}

cluster/gce/windows/smoke-test.sh

@@ -139,15 +139,9 @@ EOF
   fi
 }
 
-# Returns the name of an arbitrary Linux webserver pod.
-function get_linux_webserver_pod_name {
-  $kubectl get pods -l app=$linux_webserver_pod_label \
-    -o jsonpath='{.items[0].metadata.name}'
-}
-
 # Returns the IP address of an arbitrary Linux webserver pod.
 function get_linux_webserver_pod_ip {
-  $kubectl get pods -l app=$linux_webserver_pod_label \
+  $kubectl get pods -l app="$linux_webserver_pod_label" \
     -o jsonpath='{.items[0].status.podIP}'
 }
 
@@ -194,7 +188,7 @@ EOF
   timeout=$linux_deployment_timeout
   while [[ $timeout -gt 0 ]]; do
     echo "Waiting for $linux_command_replicas Linux $linux_command_pod_label pods to become Ready"
-    statuses=$(${kubectl} get pods -l app=$linux_command_pod_label \
+    statuses=$(${kubectl} get pods -l app="$linux_command_pod_label" \
       -o jsonpath='{.items[*].status.conditions[?(@.type=="Ready")].status}' \
       | grep "True" | wc -w)
     if [[ $statuses -eq $linux_command_replicas ]]; then
@@ -210,7 +204,7 @@ EOF
   else
     echo "ERROR: Not all $linux_command_pod_label pods became Ready"
     echo "kubectl get pods -l app=$linux_command_pod_label"
-    ${kubectl} get pods -l app=$linux_command_pod_label
+    ${kubectl} get pods -l app="$linux_command_pod_label"
     cleanup_deployments
     exit 1
   fi
@@ -218,16 +212,10 @@ EOF
 
 # Returns the name of an arbitrary Linux command pod.
 function get_linux_command_pod_name {
-  $kubectl get pods -l app=$linux_command_pod_label \
+  $kubectl get pods -l app="$linux_command_pod_label" \
     -o jsonpath='{.items[0].metadata.name}'
 }
 
-# Returns the IP address of an arbitrary Linux command pod.
-function get_linux_command_pod_ip {
-  $kubectl get pods -l app=$linux_command_pod_label \
-    -o jsonpath='{.items[0].status.podIP}'
-}
-
 # Installs test executables (ping, curl) in the Linux command pod.
 # NOTE: this assumes that there is only one Linux "command pod".
 # TODO(pjh): fix this.
@@ -318,18 +306,13 @@ EOF
   fi
 }
 
-function get_windows_webserver_pod_name {
-  $kubectl get pods -l app=$windows_webserver_pod_label \
-    -o jsonpath='{.items[0].metadata.name}'
-}
-
 function get_windows_webserver_pod_ip {
-  $kubectl get pods -l app=$windows_webserver_pod_label \
+  ${kubectl} get pods -l app="$windows_webserver_pod_label" \
     -o jsonpath='{.items[0].status.podIP}'
 }
 
 function undeploy_windows_webserver_pod {
-  ${kubectl} delete deployment $windows_webserver_deployment
+  ${kubectl} delete deployment "$windows_webserver_deployment"
 }
 
 windows_command_deployment=windows-powershell
@@ -399,17 +382,12 @@ EOF
 }
 
 function get_windows_command_pod_name {
-  $kubectl get pods -l app=$windows_command_pod_label \
+  $kubectl get pods -l app="$windows_command_pod_label" \
     -o jsonpath='{.items[0].metadata.name}'
 }
 
-function get_windows_command_pod_ip {
-  $kubectl get pods -l app=$windows_command_pod_label \
-    -o jsonpath='{.items[0].status.podIP}'
-}
-
 function undeploy_windows_command_pod {
-  ${kubectl} delete deployment $windows_command_deployment
+  ${kubectl} delete deployment "$windows_command_deployment"
 }
 
 function test_linux_node_to_linux_pod {
@@ -459,22 +437,6 @@ function test_linux_pod_to_windows_pod {
   fi
 }
 
-function test_linux_pod_to_internet {
-  echo "TEST: ${FUNCNAME[0]}"
-  local linux_command_pod
-  linux_command_pod="$(get_linux_command_pod_name)"
-  # A stable (hopefully) HTTP server provided by Cloudflare.
-  local internet_ip="1.1.1.1"
-
-  if ! $kubectl exec "$linux_command_pod" -- curl -s -m 20 \
-      "http://$internet_ip" > $output_file; then
-    cleanup_deployments
-    echo "Failing output: $(cat $output_file)"
-    echo "FAILED: ${FUNCNAME[0]}"
-    exit 1
-  fi
-}
-
 function test_linux_pod_to_k8s_service {
   echo "TEST: ${FUNCNAME[0]}"
   local linux_command_pod