T5858: Fix op-mode format for show conntrack statistics (backport #3280)

[mergify]

Change Summary

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://vyos.dev/T5858

Related PR(s)

Component(s) name

conntrack

Proposed changes

How to test

Before the fix, the output looks bad formated:

vyos@r15-left:~$ show conntrack statistics 
                CPU          Found     Invalid          Insert    Insert fail    Drop       Early drop        Errors    Search restart
-----  -------  -----------  --------  ---------------  --------  -------------  ---------  ----------------  --------  ----------------
cpu=0  found=0  invalid=174  insert=0  insert_failed=1  drop=1    early_drop=0   error=1    search_restart=0  (null)=2  (null)=0
cpu=1  found=0  invalid=73   insert=0  insert_failed=0  drop=0    early_drop=0   error=126  search_restart=0  (null)=1  (null)=0
vyos@r15-left:~$ 

After the fix:

vyos@r15-left:~$ show conntrack statistics 
CPU    Found    Invalid    Insert    Insert fail    Drop    Early drop    Errors    Search restart
-----  -------  ---------  --------  -------------  ------  ------------  --------  ----------------  --  --
0      0        174        0         1              1       0             1         0                 2   0
1      0        73         0         0              0       0             126       0                 1   0
vyos@r15-left:~$ 

Smoketest result

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

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This is an automatic backport of pull request #3280 done by [Mergify](https://mergify.com).