Implement retry on vCenter shutdown operation

[sergiojvg]

Description
Some vCenter drivers (like shutdown) can fail with the following error:

Mon May 13 21:10:51 2019 [Z0][VM][I]: New LCM state is SHUTDOWN
Mon May 13 21:10:58 2019 [Z0][VMM][I]: Command execution failed (exit code: 255): /var/lib/one/remotes/vmm/vcenter/shutdown 'vm-*' '*' 16 *
Mon May 13 21:10:58 2019 [Z0][VMM][E]: shutdown: Shutdown of VM vm-* on vCenter cluster Cluster failed due to "SystemError: A general system error occurred: Invalid fault"
Mon May 13 21:10:58 2019 [Z0][VMM][I]: /usr/lib/one/ruby/vcenter_driver/virtual_machine.rb:2539:in `rescue in shutdown'
Mon May 13 21:10:58 2019 [Z0][VMM][I]: /usr/lib/one/ruby/vcenter_driver/virtual_machine.rb:2531:in `shutdown'
Mon May 13 21:10:58 2019 [Z0][VMM][I]: /var/lib/one/remotes/vmm/vcenter/shutdown:64:in `<main>'
Mon May 13 21:10:58 2019 [Z0][VMM][I]: Failed to execute virtualization driver operation: shutdown.

This should be fixed using a retry.

Progress Status

• Branch created
• Code committed to development branch
• Testing - QA
• Documentation
• Release notes - resolved issues, compatibility, known issues
• Code committed to upstream release/hotfix branches
• Documentation committed to upstream release/hotfix branches

[sergiojvg]

PR: #3338 --> master, --> one-5.8
PR with vcenterrc file: #3350 --> master
Resolved issues: OpenNebula/docs#630 --> one-5.8-maintenance
Doc: OpenNebula/docs#631 --> master --> one-5.8