Automatic merge from submit-queue
Default host user namespace via experimental flag
@vishh @ncdc @pmorie @smarterclayton @thockin
Initial thought on the implementation https://github.com/kubernetes/kubernetes/pull/30684#issuecomment-241523425 wasn't quite right. Since we need to dereference a PVC in some cases the defaulting code didn't fit nicely in the docker manager code (would've coupled it with a kube client and would've been messy). I think passing this in via the runtime config turned out cleaner. PTAL
c76fe8dcda