Description of problem:
------------------------
When a canceled warm migration is restarted, the migration picks up from where it left off during the canceled run.
Supposing 3 precopies had been created in the canceled run, upon restarting the warm migration, the UI lists 3 precopies and it also shows that the 4th precopy is in progress.

The restart run should be treated like a fresh warm migration run and the precopies should start at 1 instead of getting added to the list of precopies from the canceled run.

Version-Release number of selected component (if applicable):
-------------------------------------------------------------
MTV 2.0.0-4


How reproducible:
-----------------
Always


Steps to Reproduce:
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1.Start a warm migration
2.Cancel the warm migration after a few precopies have been created(Supposing 3 precopies are created, the UI lists 3 precopies at this point)
3.Restart the warm migration
The UI now lists the 3 precopies from the canceled run and also shows that the 4th precopy is in progress.


Actual results:
---------------


Expected results:
-----------------


Additional info:
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I restarted a canceled warm migration plan and examined the Plan CR.The Plan CR shows precopies from previous canceled runs. This information should get reset between canceled and restarted runs so that precopies start at 1 rather than being added to the list of precopies from the canceled runs.

[nachandr]$ oc describe plan warm-migration-cancel
      Started:        2021-05-06T16:44:45Z
      Warm:
        Consecutive Failures:  0
        Failures:              0
        Next Precopy At:       2021-05-06T17:45:57Z
        Precopies:
          End:          2021-05-06T16:09:07Z   <----canceled run#1
          Start:        2021-05-06T16:08:10Z
          End:          2021-05-06T16:39:36Z   <----canceled run#2
          Start:        2021-05-06T16:38:17Z
          End:          2021-05-06T16:46:20Z   <----current run
          Start:        2021-05-06T16:45:08Z