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/network/example_cluster_dns.go

@@ -75,7 +75,7 @@ var _ = common.SIGDescribe("ClusterDns [Feature:Example]", func() {
 		return string(data)
 	}
 
-	ginkgo.It("should create pod that uses dns", func() {
+	ginkgo.It("should create pod that uses dns", func(ctx context.Context) {
 		// contrary to the example, this test does not use contexts, for simplicity
 		// namespaces are passed directly.
 		// Also, for simplicity, we don't use yamls with namespaces, but we