gometalinter -> golangci-lint migration (#3933)

{,scripts/}Makefile:
- Remove gometalinter, install golangci-lint.
- Remove distinction between tools and devtools.
  Just tools is enough.
- test_lint -> lint
  Migrating away from underscore separated names.
- Remove unnecessary targets.
- Drop tendermint/lint. Incompatbile with golangci-lint
  and no longer necessary anyway.
- Fix misleading message in go-mod-cache.
- New ci-target to avoid download tools twice.
- Run tests with -mod=readonly.

Port tools/gometalinter.json to .golangci.yml
Update CircleCI config accordingly.

Closes: #3896

x/auth/client/cli/multisign.go

@@ -105,7 +105,9 @@ func makeMultiSignCmd(cdc *amino.Codec) func(cmd *cobra.Command, args []string)
 			if ok := stdSig.PubKey.VerifyBytes(sigBytes, stdSig.Signature); !ok {
 				return fmt.Errorf("couldn't verify signature")
 			}
-			multisigSig.AddSignatureFromPubKey(stdSig.Signature, stdSig.PubKey, multisigPub.PubKeys)
+			if err := multisigSig.AddSignatureFromPubKey(stdSig.Signature, stdSig.PubKey, multisigPub.PubKeys); err != nil {
+				return err
+			}
 		}
 
 		newStdSig := auth.StdSignature{Signature: cdc.MustMarshalBinaryBare(multisigSig), PubKey: multisigPub}