Fix an unused line in applyNameOperation

... by actually using it, removing some duplication, and
perhaps micro-optimizing some memory allocations.

Signed-off-by: Miloslav Trmač <mitr@redhat.com>

utils.go

@@ -42,13 +42,14 @@ func validateMountOptions(mountOptions []string) error {
 }
 
 func applyNameOperation(oldNames []string, opParameters []string, op updateNameOperation) ([]string, error) {
-	result := make([]string, 0)
+	var result []string
 	switch op {
 	case setNames:
 		// ignore all old names and just return new names
-		return dedupeNames(opParameters), nil
+		result = opParameters
 	case removeNames:
 		// remove given names from old names
+		result = make([]string, 0, len(oldNames))
 		for _, name := range oldNames {
 			// only keep names in final result which do not intersect with input names
 			// basically `result = oldNames - opParameters`
@@ -62,11 +63,10 @@ func applyNameOperation(oldNames []string, opParameters []string, op updateNameO
 				result = append(result, name)
 			}
 		}
-		return dedupeNames(result), nil
 	case addNames:
+		result = make([]string, 0, len(opParameters)+len(oldNames))
 		result = append(result, opParameters...)
 		result = append(result, oldNames...)
-		return dedupeNames(result), nil
 	default:
 		return result, errInvalidUpdateNameOperation
 	}