syslog: T4039: Add protocol23format logging for UDP

[sever-sever]

Change Summary

Add protocol23format for rsyslog protocol UDP
Add ability to use IPv6 addresses (bracketize_ipv6) for
protocol TCP and UDP, when the protocol is configured explicitly

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/T4039

Component(s) name

syslog

Proposed changes

How to test

Config:

set system syslog host 192.168.122.11 facility all level 'all'
set system syslog host 192.168.122.11 facility all protocol 'udp'
set system syslog host 192.168.122.11 format octet-counted
set system syslog host 192.168.122.11 port '514'

Expected rsyslog conf:

*.* @192.168.122.11:514;RSYSLOG_SyslogProtocol23Format

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

[c-po]

Only a minor change request. This could be written in one line as:

{{ host_options.selectors }} @{{ host | bracketize_ipv6 }}:{{ host_options.port }}{{ ';RSYSLOG_SyslogProtocol23Format' if host_options.oct_count is defined }}

[sever-sever]

@c-po done