rconn: Queue packets for tx only if connected.

rconn: Queue packets for tx only if connected.

Until now, the rconn code would queue up packets not just while connected
but also while connecting.  This is not just unnecessary, however, it
actually causes a problem in secchan: if the secchan receives packets
from nl:0 and tries to transmit them, then they will quickly fill up
the rconn's transmit buffer (it uses a 1-packet buffer), which causes
secchan to stop reading packets from nl:0 until the buffer frees up.
That cannot happen until the connection completes.  With in-band control,
however, the connection cannot complete until we receive and process
packet_in messages in our in-band hook.  Thus, we have a deadlock.

Fixes bug #90, "Sometimes secchan has to go into fail-open mode to connect."