net/nss-pam-ldapd: use closefrom in nslcd

nslcd tries to close all file descriptors on startup. It does that by
calling close() in a loop, running down from _SC_OPEN_MAX to 0. Since
_SC_OPEN_MAX autoscales with available RAM, this can take more than a
minute on large servers. The solution is to use closefrom. Upstream
has already made that change in the master branch, but due to its slow
release cadence we're applying it here as well.

PR: 266970
Approved by: zi (maintainer)
Sponsored by: Axcient