cifs: protect access of TCP_Server_Info::{dstaddr,hostname}

Use the appropriate locks to protect access of hostname and dstaddr
fields in cifs_tree_connect() as they might get changed by other
tasks.

Signed-off-by: Paulo Alcantara (SUSE) <pc@cjr.nz>
Reviewed-by: Enzo Matsumiya <ematsumiya@suse.de>
Signed-off-by: Steve French <stfrench@microsoft.com>