ovl: remove posix_acl_default from workdir

ovl: remove posix_acl_default from workdir

Clear out posix acl xattrs on workdir and also reset the mode after
creation so that an inherited sgid bit is cleared.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Cc: <stable@vger.kernel.org>
Orabug: 26401569

(backport upstream commit c11b9fdd6a612f376a5e886505f1c54c16d8c380)
change inode_lock to mutex_lock to match the lock usage in the current
kernel.

Signed-off-by: Shan Hai <shan.hai@oracle.com>
Reviewed-by: Somasundaram Krishnasamy <somasundaram.krishnasamy@oracle.com>