[crac] RFR: Ignore open files in /var/lib/sss/mc

[Radim Vansa]

I was considering different ways to fix this - there are actually two problems:
1) how to detect that?
* This PR whitelisst all files in the directory (we could explicitly name `passwd`, `group`, `sid` and `initgroups`...)
* We could manually check all places in JDK that call `getpwuid*`, `getpwname*`, `getgrgid*`and `getgrname*` and maybe some other functions, and diff FDs opened before/after the call. However this a) has performance impact b) is prone to races
* Intercept the call: either catch syscalls (ptrace or seccomp), or patching `sss_open_cloexec` in memory, or preloading it? Rather complicated.
2) what to do with the open FD?
* Current solution is to leave this up to CRIU (or another C/R engine). Again the simplest
* We could close this; the FD is `fstat`-validated later on, so this would cause errors from these functions. We would need to patch the library, de-initializing the implementation (also risky).

Normally I would try to include a testcase but given that this is system-dependent (and the issue does not appear even in CentOS Stream 9 container) I've only did manual testing.

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Commit messages:
 - Ignore open files in /var/lib/sss/mc

Changes: https://git.openjdk.org/crac/pull/137/files
 Webrev: https://webrevs.openjdk.org/?repo=crac&pr=137&range=00
  Stats: 11 lines in 1 file changed: 11 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/crac/pull/137.diff
  Fetch: git fetch https://git.openjdk.org/crac.git pull/137/head:pull/137

PR: https://git.openjdk.org/crac/pull/137