cifs: prevent data race in smb2_reconnect()

Make sure to get an up-to-date TCP_Server_Info::nr_targets value prior
to waiting the server to be reconnected in smb2_reconnect().  It is
set in cifs_tcp_ses_needs_reconnect() and protected by
TCP_Server_Info::srv_lock.

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