[azp]: Increase timeout for VS tests (sonic-net#1988)

Workaround for some tests timing out at 99% completion

Author: prsunny

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

@@ -1,7 +1,7 @@
 parameters:
 - name: timeout
   type: number
-  default: 180
+  default: 240
 
 - name: log_artifact_name
   type: string