server+htlcswitch: check waiting-close fwdpkgs in reforwardResponses

Previously, the Switch would not check waiting-close channels' fwdpkgs
for settles or fails to reforward. This could result in a force close
in a rare edge case if a restart occurred at the wrong time. Now,
waiting-close fwdpkgs are checked and the issue is avoided.

htlcswitch/mock.go

@@ -194,6 +194,7 @@ func initSwitchWithDB(startingHeight uint32, db *channeldb.DB) (*Switch, error)
 	cfg := Config{
 		DB:                   db,
 		FetchAllOpenChannels: db.ChannelStateDB().FetchAllOpenChannels,
+		FetchAllChannels:     db.ChannelStateDB().FetchAllChannels,
 		FetchClosedChannels:  db.ChannelStateDB().FetchClosedChannels,
 		SwitchPackager:       channeldb.NewSwitchPackager(),
 		FwdingLog: &mockForwardingLog{