overlay.bats: fix the "overlay source permissions" test
overlay.bats: fix the "overlay source permissions" test

Fix a mismatch between "$permissions" being set and "$permission" being
read.

Don't expect changes made to an overlay mount in a working container to
persist between subsequent "buildah run" invocations, since they don't.

Use 'stat -c %a' rather than 'ls -l | cut -f1 -d " "' to read the
permissions on a mount upper directory, so that different versions of
"ls" appending "." to "drwxrwx---" (or not) doesn't cause unexpected
mismatches.

Create a file in the lower directory before checking that our attempt to
remove it in the upper layer succeeds.

Expect error code 1 when "buildah run $container ls" can't find a file
which we know whouldn't exist, rather than 125.

Signed-off-by: Nalin Dahyabhai <f562fcb2a0b898bf0be1afc867ea92325d8f825f@redhat.com>

projectatomic/buildah,TomSweeneyRedHat/buildah,rhatdan/buildah,rhatdan/buildah,projectatomic/buildah,TomSweeneyRedHat/buildah,projectatomic/buildah,nalind/buildah-1,rhatdan/buildah,nalind/buildah,nalind/buildah-1,nalind/buildah-1,TomSweeneyRedHat/buildah,nalind/buildah