e2e: accept context from Ginkgo

Every ginkgo callback should return immediately when a timeout occurs or the
test run manually gets aborted with CTRL-C. To do that, they must take a ctx
parameter and pass it through to all code which might block.

This is a first automated step towards that: the additional parameter got added
with

    sed -i 's/\(framework.ConformanceIt\|ginkgo.It\)\(.*\)func() {$/\1\2func(ctx context.Context) {/' \
        $(git grep -l -e framework.ConformanceIt -e ginkgo.It )
    $GOPATH/bin/goimports -w $(git status | grep modified: | sed -e 's/.* //')

log_test.go was left unchanged.

test/e2e_node/runtime_conformance_test.go

@@ -17,6 +17,7 @@ limitations under the License.
 package e2enode
 
 import (
+	"context"
 	"fmt"
 	"os"
 	"path/filepath"
@@ -67,7 +68,7 @@ var _ = SIGDescribe("Container Runtime Conformance Test", func() {
 				},
 			} {
 				testCase := testCase
-				ginkgo.It(testCase.description+" [NodeConformance]", func() {
+				ginkgo.It(testCase.description+" [NodeConformance]", func(ctx context.Context) {
 					name := "image-pull-test"
 					command := []string{"/bin/sh", "-c", "while true; do sleep 1; done"}
 					container := node.ConformanceContainer{