feat: Do not create VM if system or bootstrap disks are marked for deletion

[dlipovetsky]

What this PR does / why we need it:
Currently, if we create the VM and any of disk images are being deleted, the create task never completes, and end up waiting for task indefinitely. (We stop waiting only when the root reconcile context is cancelled, and I believe controller-runtime cancels that context only when the manager is stopped, i.e., if the process is gracefully terminated).

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Fixes # https://jira.nutanix.com/browse/NCN-101014

How Has This Been Tested?:

Please describe the tests that you ran to verify your changes. Provide instructions so we can reproduce. Please also list any relevant details for your test configuration and test output

Special notes for your reviewer:

Stacked on #489

Please confirm that if this PR changes any image versions, then that's the sole change this PR makes.

Release note:

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 13 lines in your changes missing coverage. Please review.

Project coverage is 34.50%. Comparing base (1434308) to head (0bbdd90).

Files with missing lines	Patch %	Lines
controllers/nutanixmachine_controller.go	0.00%	10 Missing ⚠️
controllers/helpers.go	0.00%	3 Missing ⚠️

Additional details and impacted files

@@                          Coverage Diff                           @@
##           jira/NCN-101014-refactor-get-image     #492      +/-   ##
======================================================================
- Coverage                               34.70%   34.50%   -0.21%     
======================================================================
  Files                                      18       18              
  Lines                                    2239     2252      +13     
======================================================================
  Hits                                      777      777              
- Misses                                   1442     1455      +13     
  Partials                                   20       20              

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