cifs: Process post session setup code in respective dialect functions.

Move the post (successful) session setup code to respective dialect routines.

For smb1, session key is per smb connection.
For smb2/smb3, session key is per smb session.

If client and server do not require signing, free session key for smb1/2/3.

If client and server require signing
  smb1 - Copy (kmemdup) session key for the first session to connection.
         Free session key of that and subsequent sessions on this connection.
  smb2 - For every session, keep the session key and free it when the
         session is being shutdown.
  smb3 - For every session, generate the smb3 signing key using the session key
         and then free the session key.

There are two unrelated line formatting changes as well.

Reviewed-by: Jeff Layton <jlayton@samba.org>
Signed-off-by: Shirish Pargaonkar <shirishpargaonkar@gmail.com>
Signed-off-by: Steve French <smfrench@gmail.com>