LU-8955 tests: exercise SELinux policy info

LU-8955 tests: exercise SELinux policy info

Add new tests 21a and 21b to sanity-selinux.sh. Goal is to test
that SELinux policy info is properly sent by the client, and
checked by the server, in the following cases:
- connection
- create
- open
- unlink
- rename
- getxattr
- setxattr
- setattr
- getattr
- symlink
- hardlink

Lustre-change: https://review.whamcloud.com/33699
Lustre-commit: 1796539799e2798caa80799e957faa03ef6af1a5

Test-Parameters: trivial testlist=sanity-selinux clientselinux
Signed-off-by: Sebastien Buisson <sbuisson@ddn.com>
Change-Id: Ibd9c5added027e12d8126641c56f21fdbc791941
Reviewed-by: Patrick Farrell <pfarrell@whamcloud.com>
Reviewed-by: Li Dongyang <dongyangli@ddn.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>
Reviewed-on: https://review.whamcloud.com/34643
Tested-by: Jenkins
Tested-by: Maloo <maloo@whamcloud.com>