mount/mount05.c: new case to test MS_BIND of mount

Create new test case for MS_BIND of mount.

Checking if file is visible from target mountpoint after bind mount.

Signed-off-by: DAN LI <li.dan@cn.fujitsu.com>
Acked-by: Cyril Hrubis <chrubis@suse.cz>
Reviewed-by: Wanlong Gao <gaowanlong@cn.fujitsu.com>