[#6758] Platform: Reuse on-premise instance once the instance got delete.

[mahendranbhat]

Description: Once we delete the onpremis universe, we have to clear the node instance so that we can use the node to create another universe.

Testing: :

1. Add instance under onpremis
2. Created the universe with the instance (failed)
3. Delete the universe .
4. Used the same instance to create another universe.

[info] Passed: Total 1141, Failed 0, Errors 0, Passed 1137, Skipped 4 [success] Total time: 707 s, completed 20 Jan, 2021 12:15:09 PM

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✅ mahendranbhat
❌ mahendra bhat

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[SergeyPotachev]

1. Cover these changes with junit tests.
2. When this problem occurs? Only when on-prem instance doesn't have public IP? Or in both cases (with and w/o public IP)? I want to know the root cause because not long time ago this functionality worked.

[mahendranbhat]

1. Cover these changes with junit tests.
2. When this problem occurs? Only when on-prem instance doesn't have public IP? Or in both cases (with and w/o public IP)? I want to know the root cause because not long time ago this functionality worked.

@SergeyPotachev

1. As mentioned in the description, checked with @Arnav15 about the test cases.
2. This happens only when the node doesn't have private ip. Currently, our on-prem universe creation is failing in our local. When you delete the universe it didn't clear the onprem instance ( to reuse it to create the new universe as shown in the ticket )

[SergeyPotachev]

1. Cover these changes with junit tests.

@SergeyPotachev

1. As mentioned in the description, checked with @Arnav15 about the test cases.

Initially I didn't pay attention on this part of comments, but now I disagree with this:
You can't write junit test for complete check of a universe deletion, but (!) you can write a test (and I can prove that it is not too difficult) to check this one function only. One test is for a case when your code is executed, another test - when it is not.
Do call the function and then check that according node details are cleaned or not cleaned. The only thing here which can be not easy - to prepare a correctly filled universe.