Fix lint errors (#1390)

* use increment and decrement operators.

* remove unnecessary else branches.

* fix package comment with leading space.

* fix receiver names.

* fix error strings.

* remove omittable code.

* remove redundant return statement.

* Revert changes (code is generated.)

* use cfg as receiver name for all config-related types.

* use lsi as the receiver name for the LastSignedInfo type.

consensus/common_test.go

@@ -101,13 +101,13 @@ func signVotes(voteType byte, hash []byte, header types.PartSetHeader, vss ...*v
 
 func incrementHeight(vss ...*validatorStub) {
 	for _, vs := range vss {
-		vs.Height += 1
+		vs.Height++
 	}
 }
 
 func incrementRound(vss ...*validatorStub) {
 	for _, vs := range vss {
-		vs.Round += 1
+		vs.Round++
 	}
 }