Suppress "cat" errors in tests
Suppress "cat" errors in tests

We invoke "cat" to determine if the mount cookie exists, and because we do
this immediately after invoking sandboxfs, the first invocation almost always
fails.  This results in test log pollution, which is pretty annoying.  Avoid
this by simply ignoring the output of these invocations.

bazelbuild/sandboxfs,bazelbuild/sandboxfs,bazelbuild/sandboxfs