IPv6: fix deploy vm issue in ipv6-only networks without VR

[weizhouapache]

Description

This PR fixes #5640 partially.

Ipv6-only shared network with offering "Quickcloud with no services" works with this PR.
Ipv6-only shared network with other offerings, which require VR, still does not work, as VR cannot start.

Types of changes

• Breaking change (fix or feature that would cause existing functionality to change)
• New feature (non-breaking change which adds functionality)
• Bug fix (non-breaking change which fixes an issue)
• Enhancement (improves an existing feature and functionality)
• Cleanup (Code refactoring and cleanup, that may add test cases)

Feature/Enhancement Scale or Bug Severity

Feature/Enhancement Scale

• Major
• Minor

Bug Severity

• BLOCKER
• Critical
• Major
• Minor
• Trivial

Screenshots (if appropriate):

How Has This Been Tested?

[weizhouapache]

@blueorangutan package

[blueorangutan]

@weizhouapache a Jenkins job has been kicked to build packages. I'll keep you posted as I make progress.

[blueorangutan]

Packaging result: ✔️ el7 ✔️ el8 ✔️ debian ✔️ suse15. SL-JID 1651

[weizhouapache]

@blueorangutan test matrix

[blueorangutan]

@weizhouapache a Trillian-Jenkins matrix job (centos7 mgmt + xs71, centos7 mgmt + vmware65, centos7 mgmt + kvmcentos7) has been kicked to run smoke tests

[blueorangutan]

Trillian test result (tid-2503)
Environment: xenserver-71 (x2), Advanced Networking with Mgmt server 7
Total time taken: 30272 seconds
Marvin logs: https://github.com/blueorangutan/acs-prs/releases/download/trillian/pr5648-t2503-xenserver-71.zip
Smoke tests completed. 91 look OK, 0 have errors
Only failed tests results shown below:

Test	Result	Time (s)	Test File

[blueorangutan]

Trillian test result (tid-2504)
Environment: kvm-centos7 (x2), Advanced Networking with Mgmt server 7
Total time taken: 31188 seconds
Marvin logs: https://github.com/blueorangutan/acs-prs/releases/download/trillian/pr5648-t2504-kvm-centos7.zip
Smoke tests completed. 91 look OK, 0 have errors
Only failed tests results shown below:

Test	Result	Time (s)	Test File

[blueorangutan]

Trillian test result (tid-2505)
Environment: vmware-65u2 (x2), Advanced Networking with Mgmt server 7
Total time taken: 34106 seconds
Marvin logs: https://github.com/blueorangutan/acs-prs/releases/download/trillian/pr5648-t2505-vmware-65u2.zip
Smoke tests completed. 91 look OK, 0 have errors
Only failed tests results shown below:

Test	Result	Time (s)	Test File

[sureshanaparti]

code LGTM

[DaanHoogland]

clgtm

[GabrielBrascher]

Thanks for the PR @weizhouapache.
+1 on Daan's suggestion on extracting those lines into a method.

Code LGTM.