selinux: documentation and file permission fixes

Clean up some mistakes in javadocs and test failure messages for various
SELinux tests. Additionally, fixup some file permission problems.

This is a partial redo of 879ed91e4a338cae998c5d59f31ce87ab8325ec4, but
carrying over only the cleanup portions.

Test: CTS compiles.
Change-Id: Ib4ffe3962eb8d22e39701bbe1949524aaf07d379
8 files changed