[ci] Continue on error when running test. (#757)

Unblock pipeline when running CI build and scheduled build.

Author: liushilongbuaa

.azure-pipelines/test-docker-sonic-vs-template.yml

@@ -87,6 +87,8 @@ jobs:
 
       rm -rf $(Build.ArtifactStagingDirectory)/download
     displayName: "Run vs tests"
+    ${{ if ne(variables['Build.Reason'], 'PullRequest') }}:
+      continueOnError: true
 
   - task: PublishTestResults@2
     inputs: