Fix bug in proc_test.
Fix bug in proc_test.

TestNoDuplicates is racy as it tries to read the /proc file system
while the test is running. But it's possible that from the time a
directory entries are read and each entry processed something could
change and in some cases the entry being processed could have been
deleted. In such cases we should not fail the test but just
ignore the error and move on.

PiperOrigin-RevId: 267483094

google/gvisor,google/gvisor,google/gvisor,google/gvisor,google/gvisor,google/gvisor,google/gvisor,google/gvisor