LDAP: match on tuples instead of the #eldap_search_result record for OTP 24.3 compat

[michaelklishin]

In erlang/otp#5538, the eldap_search_result
record structure has changed:
https://github.com/erlang/otp/pull/5538/files#diff-30e064e89b115da7e974f229ed5c92f28e489da679ef42f17e70b9e7cf874179R24

It does have a default but for code
compiled on, say, Erlang 23.0, which is the case for current RabbitMQ
releases, it would still be a breaking change resulting in
case expression matching failures (a case_clause).

Note that CI would not hit this issue. In order to reproduce, you have to build on Erlang pre-24.3 but run on 24.3.

Closes #4284.

[lukebakken]

@michaelklishin should this API change have been released in a minor OTP version? 🤔 https://github.com/erlang/otp/pull/5538/files#diff-30e064e89b115da7e974f229ed5c92f28e489da679ef42f17e70b9e7cf874179R21-R24

Seems like it should have waited until OTP 25.

[michaelklishin]

@lukebakken if you compile on 24.3 and run on 24.3, you wouldn't run into this. So I think it was OK to backport for the general Erlang/Elixir user base, just not for projects such as RabbitMQ. We've been there before.

[lukebakken]

In my local environment eldap_search_result is always a tuple with two elements, not three. So, I can't reproduce the original issue. I applied the patch and my LDAP environment continued to work correctly (as expected).

This is an easy-to-understand fix for a well-reported issue, so 👍