CA-393199: Disable external auth should clean pbis cache

[liulinC]

The domain information is cached by PBIS. Such cache can help to accelerate query of domain information.

However, the cache data should be cleaned during disable external auth to make sure

• release cache as the domain is left
• rejoin domain refresh all the domain information

[lindig]

The exception should be logged to help diagnose the problem.

[liulinC]

The exception should be logged to help diagnose the problem.

I ignore the exception by intention as we do not really care about the error, (and ignored)
this is best to have clean.
But I have updated the code anyway as it always better to log errors.

[Vincent-lau]

Grammar issue, but I think this is confusing:

in the commit message you mean:
"release cache as the domain has left" right?

[psafont]

Requesting changes since linding's comment is waiting

[liulinC]

Grammar issue, but I think this is confusing:

in the commit message you mean: "release cache as the domain has left" right?

well, leave domain is part of disable external auth.
Thanks for the comments, I have updated the comment to clarify this.

[liulinC]

Sorry, I accidentally create a new branch in this repo, (instead of my private repo).
Will delete the branch after this merge.

[lindig]

1060 |         |> debug "Got error cleaning pbis cache, ignore the error %s"
                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Error: This expression has type string -> unit
       but an expression was expected of type (exn -> string) -> 'a
       Type string is not compatible with type exn -> string 
make: *** [Makefile:10: build] Error 1

[lindig]

This was not tested

[liulinC]

tested

The original code was test in my local env,
I did not re-test Printexc.to_string as it is low risk.
Thanks compiler detected the grammar issue.

[robhoes]

I believe @psafont 's request has been addressed, so I'll dismiss his review and merge the PR.

Feedback has been addressed.