fix shellcheck failure

hack/dev-push-hyperkube.sh

@@ -26,16 +26,16 @@ set -o errexit
 set -o nounset
 set -o pipefail
 
-KUBE_ROOT="$(dirname "${BASH_SOURCE}")/.."
+KUBE_ROOT="$(dirname "${BASH_SOURCE[0]}")/.."
 source "${KUBE_ROOT}/build/common.sh"
 
 if [[ -z "${REGISTRY:-}" ]]; then
 	echo "REGISTRY must be set"
-	exit -1
+	exit 1
 fi
 if [[ -z "${VERSION:-}" ]]; then
 	echo "VERSION must be set"
-	exit -1
+	exit 1
 fi
 
 IMAGE="${REGISTRY}/hyperkube-amd64:${VERSION}"