misc: go vet fixes

These are some code problems flagged by `go vet` that shouldn't affect
correctness at all.

Signed-off-by: Hank Donnay <[email protected]>

digest.go

@@ -127,9 +127,7 @@ func (d *Digest) Scan(i interface{}) error {
 		return nil
 	default:
 		return &DigestError{msg: fmt.Sprintf("invalid digest type: %T", v)}
-
 	}
-	panic("the default case should return before this panic is reached.")
 }
 
 // Value implements driver.Valuer.

rhel/updaterset.go

@@ -52,7 +52,7 @@ type Factory struct {
 }
 
 type FactoryConfig struct {
-	URL string `json:"url", yaml:"url"`
+	URL string `json:"url" yaml:"url"`
 }
 
 func (f *Factory) Configure(ctx context.Context, cfg driver.ConfigUnmarshaler, c *http.Client) error {

rpm/packagescanner.go

@@ -336,7 +336,4 @@ func parsePackage(ctx context.Context, log zerolog.Logger, src map[string]*clair
 			return nil, err
 		}
 	}
-
-	// Should have cleanly returned when io.EOF was hit.
-	panic("unreachable")
 }