tests/valgrind: Check for leaking file descriptors

[btriller]

Let valgrind track fds to catch unclosed file descriptors. That would have catched bug in #5722.

[larsewi]

Thanks @btriller 🚀

I see that your change found another leaking file descriptor:

 ---snip---
==31286== FILE DESCRIPTORS: 4 open (3 std) at exit.
==31286== Open file descriptor 3: /var/cfengine/state/am_policy_hub
==31286==    at 0x4D528B4: creat (creat64.c:28)
==31286==    by 0x48B5CF5: WriteAmPolicyHubFile (bootstrap.c:218)
==31286==    by 0x490402E: GenericAgentDiscoverContext (generic_agent.c:1092)
==31286==    by 0x11A008: main (cf-agent.c:296)
 ---snip---

Do you want to fix it, or do you want us to take a look at it?

[btriller]

Do you want to fix it, or do you want us to take a look at it?

Please go ahead.

[larsewi]

There's still a leaked file descriptor. I will have to get back to this next week @btriller

[larsewi]

@btriller I investigated the remaining file descriptor leak but wasn't able to resolve it within the current sprint scope. I've created ticket CFE-4593 to track this issue for future prioritization when we have additional resources to throw at it.

I'm closing this PR for now, with the plan to reopen it once we can allocate some time to address it properly. Thanks again for the contribution 🚀