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

p2p/conn/connection_test.go

@@ -57,7 +57,8 @@ func TestMConnectionSendFlushStop(t *testing.T) {
 		msgB := make([]byte, aminoMsgLength)
 		_, err := server.Read(msgB)
 		if err != nil {
-			t.Fatal(err)
+			t.Error(err)
+			return
 		}
 		errCh <- err
 	}()