cifs: clear server inode number flag while autodisabling

Fix the commit ec06aedd that intended to turn off querying for server inode
numbers when server doesn't consistently support inode numbers. Presumably
the commit didn't actually clear the CIFS_MOUNT_SERVER_INUM flag, perhaps a
typo.

Signed-off-by: Suresh Jayaraman <sjayaraman@suse.de>
Acked-by: Jeff Layton <jlayton@redhat.com>
Cc: Stable <stable@kernel.org>
Signed-off-by: Steve French <sfrench@us.ibm.com>