cifs: update ip_addr for ses only for primary chan setup

We update ses->ip_addr whenever we do a session setup.
But this should happen only for primary channel in mchan
scenario.

Signed-off-by: Shyam Prasad N <sprasad@microsoft.com>
Reviewed-by: Paulo Alcantara (SUSE) <pc@cjr.nz>
Signed-off-by: Steve French <stfrench@microsoft.com>