Fix identity domain destruction by deactivating the identity domain before deletion

[F21]

The current implementation for deleting an identity domain attempts to call delete on it immediately. This will fail because an identity domain must be deactivated before it can be deleted. See API reference: https://docs.oracle.com/en-us/iaas/api/#/en/identity/20160918/Domain/DeleteDomain

This PR fixes the issue by deactivating the identity domain and waiting until it is marked as deactivated before attempting to delete it.

Closes #1781

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[thpham]

Can someone from Oracle can take this over even the PR contributor has not signed the OCA !?
This is blocking us. It could be very easy to re-submit the PR and being able to be reviewed/approved !

[F21]

@thpham, oracle has approved my OCA, but it seems they don't really accept external contributions for this project.

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