system connection remove: use Args function to validate

[Luap99]

Using the ExactArgs(1) function is better because we have less duplication of the error text and the ValidArgsFunction uses that to suggest shell completion. The command before this commit would suggest connection names even if there was already one arg on the cli set.

Does this PR introduce a user-facing change?

None

[openshift-ci]

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[edsantiago]

Will this PR resolve the following flake?

   [08:08:53.654983172] $ /home/esm/src/atomic/2018-02.podman/libpod/bin/podman __completeNoDesc  commit                                                        
   [08:08:54.794829256] [Debug] [Error] could not find container 1d7c59f6127f23f60b0d1aa061d76c0e6d3570d5c568c08f908e9e378a53e105 pod (id 09b5f4e71d6ac3fd532b92
b287e3e3a4e639dc6fec4e8a5637f514333915fbfc) in state: no such pod                                                                                               
   :4                                                                                                                                                           
   Completion ended with directive: ShellCompDirectiveNoFileComp                                                                                                
   #/vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv                                                                                                              
   #|     FAIL:  commit: actual container listed in suggestions                                                                                                 
   #| expected: '.*-c_t112-xgnokdit                                                                                                                             
   ' (using expr)                                                                                                                                               
   #|   actual: '[Debug] [Error] could not find container 1d7c59f6127f23f60b0d1aa061d76c0e6d3570d5c568c08f908e9e378a53e105 pod (id 09b5f4e71d6ac3fd532b92b287e3e
3a4e639dc6fec4e8a5637f514333915fbfc) in state: no such pod'                                                                                                     
   #|         > ':4'                                                                                                                                            
   #|         > 'Completion ended with directive: ShellCompDirectiveNoFileComp'                                                                                 
   #\^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

(one-off just now, on my laptop, with #23325 but without #23326. And, sorry, I did not save logs. Will apply #23326 and keep trying, with logs).

[edsantiago]

Test failure is real; new code needs to account for --all

[Luap99]

Test failure is real; new code needs to account for --all

Oh how did I miss that, of course there was a reason for it in the first place.

[Luap99]

(one-off just now, on my laptop, with #23225 but without #23226. And, sorry, I did not save logs. Will apply #23226 and keep trying, with logs).

Numbers are off?

[edsantiago]

Ugh. Sorry, fixed. Anyhow, no, that failure is pretty persistent, I'm trying to reproduce it and will file an issue

[Luap99]

Nah that would still be #23282, my PR should definitely fix the no such pod error, just because I added more context doesn't mean the cause is different. Something must be weird about how we lock things there

[Luap99]

@containers/podman-maintainers PTAL This is needed for the parallel sys test work.

[ashley-cui]

LGTM

[edsantiago]

LGTM and I'm not seeing the otherwise-almost-constant completion test failure. Thank you!

/lgtm