smb: server: make use of smbdirect_connection_{create,destroy}_qp()

smb: server: make use of smbdirect_connection_{create,destroy}_qp()

It's good a use common code for this and it will allow us
to share more code in the next steps.

Calling ib_drain_qp() twice is ok.

Cc: Namjae Jeon <linkinjeon@kernel.org>
Cc: Steve French <smfrench@gmail.com>
Cc: Tom Talpey <tom@talpey.com>
Cc: linux-cifs@vger.kernel.org
Cc: samba-technical@lists.samba.org
Signed-off-by: Stefan Metzmacher <metze@samba.org>
Acked-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>