multi: make watchtower client/server DBs remote compatible

The final database that needs to be made remote compatible is the
watchtower server and client database.
They are handled a bit differently because both of them are not always
active, only when specifically turned on in the config.

server.go

@@ -352,8 +352,7 @@ func noiseDial(idKey keychain.SingleKeyECDH,
 // newServer creates a new instance of the server which is to listen using the
 // passed listener address.
 func newServer(cfg *Config, listenAddrs []net.Addr,
-	dbs *databaseInstances,
-	towerClientDB wtclient.DB, cc *chainreg.ChainControl,
+	dbs *databaseInstances, cc *chainreg.ChainControl,
 	nodeKeyDesc *keychain.KeyDescriptor,
 	chansToRestore walletunlocker.ChannelsToRecover,
 	chanPredicate chanacceptor.ChannelAcceptor,
@@ -1306,7 +1305,7 @@ func newServer(cfg *Config, listenAddrs []net.Addr,
 			SecretKeyRing:  s.cc.KeyRing,
 			Dial:           cfg.net.Dial,
 			AuthDial:       authDial,
-			DB:             towerClientDB,
+			DB:             dbs.towerClientDB,
 			Policy:         policy,
 			ChainHash:      *s.cfg.ActiveNetParams.GenesisHash,
 			MinBackoff:     10 * time.Second,
@@ -1329,7 +1328,7 @@ func newServer(cfg *Config, listenAddrs []net.Addr,
 			SecretKeyRing:  s.cc.KeyRing,
 			Dial:           cfg.net.Dial,
 			AuthDial:       authDial,
-			DB:             towerClientDB,
+			DB:             dbs.towerClientDB,
 			Policy:         anchorPolicy,
 			ChainHash:      *s.cfg.ActiveNetParams.GenesisHash,
 			MinBackoff:     10 * time.Second,