multi: add fmgr.Manager interface, change usage in peer to use Manager

This gets rid of several config functions in the peer and should pave
the way for easier testing of the funding manager and peer.

fmgr/interfaces.go

@@ -0,0 +1,20 @@
+package fmgr
+
+import (
+	"github.com/lightningnetwork/lnd/lnpeer"
+	"github.com/lightningnetwork/lnd/lnwire"
+)
+
+// Manager is an interface that describes the basic operation of a funding
+// manager. It should at a minimum process a subset of lnwire messages that
+// are denoted as funding messages.
+type Manager interface {
+	// ProcessFundingMsg processes a funding message represented by the
+	// lnwire.Message parameter along with the Peer object representing a
+	// connection to the counterparty.
+	ProcessFundingMsg(lnwire.Message, lnpeer.Peer)
+
+	// IsPendingChannel is used to determine whether to send an Error message
+	// to the funding manager or not.
+	IsPendingChannel([32]byte, lnpeer.Peer) bool
+}