nss_compat: internal_end*ent may clobber errno, hiding ERANGE [BZ #25976]
During cleanup, before returning from get*_r functions, the end*ent
calls must not change errno. Otherwise, an ERANGE error from the
underlying implementation can be hidden, causing unexpected lookup
failures. This commit introduces an internal_end*ent_noerror
function which saves and restore errno, and marks the original
internal_end*ent function as warn_unused_result, so that it is used
only in contexts were errors from it can be handled explicitly.
Reviewed-by: DJ Delorie <dj@redhat.com>