lnd: fix issues reported by golint+govet

github.com/lightningnetwork/lnd  master ✗

                                           0m ◒
▶ golint
htlcswitch.go:292:4: should replace numUpdates += 1 with numUpdates++
htlcswitch.go:554:6: var onionId should be onionID
htlcswitch.go:629:7: var onionId should be onionID
lnd_test.go:133:1: context.Context should be the first parameter of a
function
lnd_test.go:177:1: context.Context should be the first parameter of a
function
networktest.go:84:2: struct field nodeId should be nodeID
peer.go:1704:16: should omit 2nd value from range; this loop is
equivalent to `for invoice := range ...`
rpcserver.go:57:6: func newRpcServer should be newRPCServer

github.com/lightningnetwork/lnd  master ✗

                                        9m ⚑ ◒  ⍉
▶ go vet
features.go:12: github.com/lightningnetwork/lnd/lnwire.Feature
composite literal uses unkeyed fields
fundingmanager.go:380: no formatting directive in Errorf call
exit status 1

rpcserver.go

@@ -53,8 +53,8 @@ type rpcServer struct {
 // LightningServer gRPC service.
 var _ lnrpc.LightningServer = (*rpcServer)(nil)
 
-// newRpcServer creates and returns a new instance of the rpcServer.
-func newRpcServer(s *server) *rpcServer {
+// newRPCServer creates and returns a new instance of the rpcServer.
+func newRPCServer(s *server) *rpcServer {
 	return &rpcServer{server: s, quit: make(chan struct{}, 1)}
 }