Update chown/permission_error test to work, even when uid/gid is 1000.

Previously, this test assumed that calling chown 1000:1000 file.txt was
invalid. That turns out to be valid if the current uid/gid is 1000/1000.

Update the test to take uid/gid as config consts and then add one to both to
get invalid uid/gid value.
Merge pull request #888 from thomasvandoren/robustify-chown-test

Update chown/permission_error test to work, even when uid/gid is 1000.

Previously, this test assumed that calling `chown 1000:1000 file.txt` was
invalid. That turns out to be valid if the current uid/gid is 1000/1000.

Update the test to take uid/gid as config consts and then add one to both to
get invalid uid/gid value.