Automatic merge from submit-queue volume controller: add configurable integration test to stress the binder The test tries to bind configured nr. of PVs to the same nr. of PVCs. '100' is used by default, which should take ~1-3 seconds (depends on log level). Periodic sync is needed in rare cases, which may add another 10 seconds. - cache from #25881 will help here and sync should not be needed at all. The test is configurable and may be reused to measure binder performance. Set KUBE_INTEGRATION_PERSISTENTVOLUME_* env. variables as described in persistent_volume_test.go and run the tests: ``` # compile $ cd test/integration $ godep go test -tags 'integration no-docker' -c # run the tests $ KUBE_INTEGRATION_PERSISTENTVOLUME_SYNC_PERIOD=10s KUBE_INTEGRATION_PERSISTENTVOLUME_OBJECTS=1000 time ./integration.test -test.run TestPersistentVolumeMultiPVsPVCs -v 2 ``` Log level '2' is useful to get timestamps of various events like 'TestPersistentVolumeMultiPVsPVCs: start' and 'TestPersistentVolumeMultiPVsPVCs: claims are bound'.