ipsec: T3948: Add CLI site-to-site peer connection-type none

[sever-sever]

Change Summary

Add VPN ipsec peer connection-type 'none'

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Code style update (formatting, renaming)
• Refactoring (no functional changes)
• Migration from an old Vyatta component to vyos-1x, please link to related PR inside obsoleted component
• Other (please describe):

Related Task(s)

• https://phabricator.vyos.net/T3948

Component(s) name

vpn, ipsec

Proposed changes

How to test

Add peer connection-type 'none'

set vpn ipsec site-to-site peer 192.168.122.14 connection-type none

Swanctl configuration:

vyos@r11-roll:~$ sudo cat /etc/swanctl/swanctl.conf | grep start
                start_action = none

Checklist:

• I have read the CONTRIBUTING document
• I have linked this PR to one or more Phabricator Task(s)
• I have run the components SMOKETESTS if applicable
• My commit headlines contain a valid Task id
• My change requires a change to the documentation
• I have updated the documentation accordingly