add staticcheck linting (#3828)

cleanup to add linter

    grpc change:
        https://godoc.org/google.golang.org/grpc#WithContextDialer
        https://godoc.org/google.golang.org/grpc#WithDialer
        grpc/grpc-go#2627
    prometheous change:
        due to UninstrumentedHandler, being deprecated in the future
    empty branch = empty if or else statement
        didn't delete them entirely but commented
        couldn't find a reason to have them
    could not replicate the issue #3406
        but if want to keep it commented then we should comment out the if statement as well

tools/tm-monitor/mock/eventmeter.go

@@ -54,7 +54,7 @@ func (c *RpcClient) Call(method string, params map[string]interface{}, result in
 	}
 
 	rv, rt := reflect.ValueOf(result), reflect.TypeOf(result)
-	rv, rt = rv.Elem(), rt.Elem()
+	rv, _ = rv.Elem(), rt.Elem()
 	rv.Set(reflect.ValueOf(s))
 
 	return s, nil