build+routerrpc+lncli: remove routerrpc conditional compilation

Dockerfile

@@ -18,7 +18,7 @@ RUN apk add --no-cache --update alpine-sdk \
 &&  cd /go/src/github.com/lightningnetwork/lnd \
 &&  git checkout $checkout \
 &&  make \
-&&  make install tags="signrpc walletrpc chainrpc invoicesrpc routerrpc"
+&&  make install tags="signrpc walletrpc chainrpc invoicesrpc"
 
 # Start a new, final image.
 FROM alpine as final