drbd: Restore late assigning of tconn->data.sock and meta.sock

With commit from Mon Mar 28 16:33:12 2011 +0200
"drbd: drbd_connect(): Initialize struct drbd_socket before sending anything"

tconn->data.sock and tconn->meta.sock get assigned early, in
conn_connect.

The early assigning can trigger an OOPS, because it may released the socket
without acquiring the mutex protecting the socket. An other thread (worker)
might use setsockopt() on the socket while it gets free()ed.

Restored the (proven) 8.3 behavior of assigning these sockets after the two
connections are established.

Credits for reporting the issue are going to Arne Redlich.

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>