cifs: consolidate reconnect logic in smb_init routines

There's a large cut and paste chunk of code in smb_init and
small_smb_init to handle reconnects. Break it out into a separate
function, clean it up and have both routines call it.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>