audit: keep inode pinned

commit 799b601451b21ebe7af0e6e8f6e2ccd4683c5064 upstream.

Audit rules disappear when an inode they watch is evicted from the cache.
This is likely not what we want.

The guilty commit is "fsnotify: allow marks to not pin inodes in core",
which didn't take into account that audit_tree adds watches with a zero
mask.

Adding any mask should fix this.

Fixes: 90b1e7a5 ("fsnotify: allow marks to not pin inodes in core")
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Paul Moore <pmoore@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>