peer: fix bug in handshake wherein RevokeAndAck would be sent first
peer: fix bug in handshake wherein RevokeAndAck would be sent first

This commit fixes a bug in the opening handshake between to peers. The
bug would arise when on or many channels were active between a node
establishing a new connection. The htlcManager goroutines will
immediately attempt to extend the revocation window once they’re
active. However, at this time, the init message may not yet have been
sent as the two executions are in distinct goroutines.

We fix this bug by manually writing the init message directly to the
socket, rather than traveling through the queueHandler goroutine. With
this, we ensure that the init message is _always_ sent first.

LightningNetwork/lnd,AndrewSamokhvalov/lnd,aakselrod/lnd,AndrewSamokhvalov/lnd,ddustin/lnd,LightningNetwork/lnd,ddustin/lnd,aakselrod/lnd