socket: propogate connect failure in socket_event_handler

This patch prevents spurious handling of pollin/pollout events on an
'un-connected' socket, when outgoing packets to its remote endpoint are
'dropped' using iptables(8) rules.

For eg,
 iptables -I OUTPUT -p tcp --dport 24007 -j DROP


Change-Id: I1d3f3259dc536adca32330bfb7566e0b9a521e3c
BUG: 1048188
Signed-off-by: Krishnan Parthasarathi <kparthas@redhat.com>
Reviewed-on: http://review.gluster.org/6627
Reviewed-by: Anand Avati <avati@redhat.com>
Tested-by: Anand Avati <avati@redhat.com>

rpc/rpc-transport/socket/src/socket.c

@@ -2195,7 +2195,7 @@ unlock:
                 rpc_transport_notify (this, event, this);
         }
 out:
-        return 0;
+        return ret;
 }