Simplify the test for chown with uid==-1, gid==-1

[asomers]

• Bug fix: the second chown should've been directed at the symlink
• Use users 0/65534 instead of 65534/65532. There's nothing special about uid 0 for this tests's purposes. Using uid 0 as the file owner allows skipping some setup tests and eliminating an extra user.
• Eliminate a step that basically just asserts "chown follows symlinks"
• Eliminate a step that basically just asserts "stat follows symlinks"

This change eliminates user 65532 from the test suite.

[asomers]

cc @musikid