Change to pass Schema compare Operation id from ADS

[udeeshagautam]

This PR contains

Changes for Schema compare operation id to be passed from ADS so that

1. ADS knows the operation id to cancel if needed without having to wait for operation to return
2. We can have only one id per SC page so that only the open page's result is stored in memory not the previous compares.
   Test fix to add Cancel call in service call test

[kisantia]

Thanks for adding the open scmp service call to the test :)

[coveralls]

Coverage increased (+0.05%) to 76.22% when pulling 5c06048 on bug/schemacompare-CancelCallFix into 3e1f186 on master.