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

types/genesis_test.go

@@ -68,7 +68,7 @@ func TestGenesisGood(t *testing.T) {
 	genDoc.ConsensusParams.Block.MaxBytes = 0
 	genDocBytes, err = cdc.MarshalJSON(genDoc)
 	assert.NoError(t, err, "error marshalling genDoc")
-	genDoc, err = GenesisDocFromJSON(genDocBytes)
+	_, err = GenesisDocFromJSON(genDocBytes)
 	assert.Error(t, err, "expected error for genDoc json with block size of 0")
 
 	// Genesis doc from raw json

types/validator_set.go

@@ -619,10 +619,11 @@ func (vals *ValidatorSet) VerifyCommit(chainID string, blockID BlockID, height i
 		// Good precommit!
 		if blockID.Equals(precommit.BlockID) {
 			talliedVotingPower += val.VotingPower
-		} else {
-			// It's OK that the BlockID doesn't match.  We include stray
-			// precommits to measure validator availability.
 		}
+		// else {
+		// It's OK that the BlockID doesn't match.  We include stray
+		// precommits to measure validator availability.
+		// }
 	}
 
 	if talliedVotingPower > vals.TotalVotingPower()*2/3 {
@@ -703,10 +704,11 @@ func (vals *ValidatorSet) VerifyFutureCommit(newSet *ValidatorSet, chainID strin
 		// Good precommit!
 		if blockID.Equals(precommit.BlockID) {
 			oldVotingPower += val.VotingPower
-		} else {
-			// It's OK that the BlockID doesn't match.  We include stray
-			// precommits to measure validator availability.
 		}
+		// else {
+		// It's OK that the BlockID doesn't match.  We include stray
+		// precommits to measure validator availability.
+		// }
 	}
 
 	if oldVotingPower <= oldVals.TotalVotingPower()*2/3 {