Analyze nightly failed cases

1. Modify delete repo button locator;
2. Modify verifcation for GC log result message;
3. Modify locator for tag retention.
4. Add empty Trivy pipeline.

Signed-off-by: danfengliu <danfengl@vmware.com>

tests/robot-cases/Group1-Nightly/Common_GC.robot

@@ -38,7 +38,7 @@ Test Case - Garbage Collection
     ${rc}  ${output}=  Run And Return Rc And Output  curl -u ${HARBOR_ADMIN}:${HARBOR_PASSWORD} -i --insecure -H "Content-Type: application/json" -X GET "https://${ip}/api/v2.0/system/gc/1/log"
     Log To Console  ${output}
     Should Be Equal As Integers  ${rc}  0
-    Should Contain  ${output}  3 blobs marked, 0 blobs and 0 manifests eligible for deletion
+    Should Contain  ${output}  0 blobs marked, 3 blobs and 0 manifests eligible for deletion
     Should Contain  ${output}  success to run gc in job.
 
     Close Browser

tests/robot-cases/Group1-Nightly/Trivy.robot

@@ -0,0 +1,29 @@
+
+// Copyright (c) 2017 VMware, Inc. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//    http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+*** Settings ***
+Documentation  Harbor BATs
+Resource  ../../resources/Util.robot
+Default Tags  Nightly
+
+*** Variables ***
+${HARBOR_URL}  https://${ip}
+${SSH_USER}  root
+${HARBOR_ADMIN}  admin
+
+*** Test Cases ***
+Test Case - Get Harbor Version
+#Just get harbor version and log it
+    Get Harbor Version