Fix update k8s resource always trigger upgrade v1 (#412)

* Revert "Fix cannot retry upgrade gsk when previous upgrade fails v1 (#410)"

This reverts commit a9def41.

* set the correct gsk version/release at resource read

gridscale/resource_gridscale_k8s.go

@@ -374,18 +374,30 @@ func deriveK8sTemplateFromResourceData(client *gsclient.Client, d *schema.Resour
 	releaseInterface, isReleaseSet := d.GetOk("release")
 	release := releaseInterface.(string)
 
-	if isVersionSet {
-		derivationTypesRequested += 1
-		derivationType = "version"
-	}
+	if !d.IsNewResource() { // case if update of resource is requested
+		if isVersionSet && d.HasChange("version") {
+			derivationTypesRequested += 1
+			derivationType = "version"
+		}
 
-	if isReleaseSet {
-		derivationTypesRequested += 1
-		derivationType = "release"
-	}
+		if isReleaseSet && d.HasChange("release") {
+			derivationTypesRequested += 1
+			derivationType = "release"
+		}
+	} else { // case if creation of resource is requested
+		if isVersionSet {
+			derivationTypesRequested += 1
+			derivationType = "version"
+		}
 
-	if derivationTypesRequested == 0 {
-		return nil, errors.New("either \"release\" or \"gsk_version\" has to be defined")
+		if isReleaseSet {
+			derivationTypesRequested += 1
+			derivationType = "release"
+		}
+
+		if derivationTypesRequested == 0 {
+			return nil, errors.New("either \"release\" or \"gsk_version\" has to be defined")
+		}
 	}
 
 	if derivationTypesRequested > 1 {