cifs: Always resolve hostname before reconnecting

commit 28eb24ff75c5ac130eb326b3b4d0dcecfc0f427d upstream.

In case a hostname resolves to a different IP address (e.g. long
running mounts), make sure to resolve it every time prior to calling
generic_ip_connect() in reconnect.

Suggested-by: Steve French <stfrench@microsoft.com>
Signed-off-by: Paulo Alcantara <palcantara@suse.de>
Signed-off-by: Steve French <stfrench@microsoft.com>
Signed-off-by: Pavel Shilovsky <pshilov@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>