runtimes/google/ipc/stream/vc: Fix vc_test flakiness.

I have noticed that vc_test is occasionally flaky. I think it is because
we panic in pipeloop, where the program may just happen to be when we close
VCs.

Making these just log instead of panic should fix the issue.

Change-Id: Idb7659f770ef821666d41d118aecd46baa784091
1 file changed