(#18026) Don't warn on failed stats for selinux context

We try to stat files to determine the default selinux context. This may happen
before the file exists. A warning was recently added, and it seems to just be
confusing and noisy, so this removes it.
Merge pull request #1396 from pcarlisle/ticket/180260-selinux-stat-warnings

(#18026) Don't warn on failed stats for selinux context