[Draft] VR: allow outgoing traffic from Remote access VPN clients

[weizhouapache]

Description

This PR enables VR to allow outgoing traffic from Remote access VPN clients via CloudStack VR.

This PR is a draft. Ideally there is a global/account configuration, or new property of remote access VPN (similar as remote.access.vpn.client.iprange)

Remote access vpn (setup by L2tp in CloudStack VR) does not support split tunneling. Where are two options when user connects to the RAV server

• Do not use the VPN connection for the client. User has to manually add static route to the VMs on guest network.
• Use the VPN connection for the client. All traffic will go through the RAV server (cloudstack VR). Currently, if uses choose this option, the RAV client will lose connection to the Internet. This PR fixes the issue.

Note, there is no option for L2TP clients to "Use the VPN connection only on the resource of the network".

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)
• build/CI
• test (unit or integration test code)

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?

How did you try to break this feature and the system with this change?

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 16.03%. Comparing base (e57a82a) to head (1497d59).

Additional details and impacted files

@@             Coverage Diff              @@
##               4.20   #10083      +/-   ##
============================================
- Coverage     16.03%   16.03%   -0.01%     
  Complexity    12814    12814              
============================================
  Files          5637     5637              
  Lines        493506   493506              
  Branches      59831    59831              
============================================
- Hits          79129    79127       -2     
- Misses       405601   405602       +1     
- Partials       8776     8777       +1     

Flag	Coverage Δ
uitests	4.02% <ø> (ø)
unittests	16.87% <ø> (-0.01%)	⬇️

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[blueorangutan]

Packaging result [SF]: ✔️ el8 ✔️ el9 ✔️ debian ✔️ suse15. SL-JID 11804

[Pearl1594]

@weizhouapache is this ready for review?