linter: (1/2) enable errcheck (#5064)

## Description

partially cleanup in preparation for errcheck

i ignored a bunch of defer errors in tests but with the update to go 1.14 we can use `t.Cleanup(func() { if err := <>; err != nil {..}}` to cover those errors, I will do this in pr number two of enabling errcheck.

ref #5059

libs/log/tmfmt_logger.go

@@ -107,7 +107,7 @@ KeyvalueLoop:
 
 		err := enc.EncodeKeyval(keyvals[i], keyvals[i+1])
 		if err == logfmt.ErrUnsupportedValueType {
-			enc.EncodeKeyval(keyvals[i], fmt.Sprintf("%+v", keyvals[i+1]))
+			enc.EncodeKeyval(keyvals[i], fmt.Sprintf("%+v", keyvals[i+1])) //nolint:errcheck // no need to check error again
 		} else if err != nil {
 			return err
 		}