[SSSD] [sssd PR#330][opened] ad_account_can_shortcut: shortcut if ID is unknown

[sumit-bose]

   URL: https://github.com/SSSD/sssd/pull/330
Author: sumit-bose
 Title: #330: ad_account_can_shortcut: shortcut if ID is unknown
Action: opened

PR body:
"""
If sss_idmap_unix_to_sid() returns an error we can assume that the given
POSIX ID is not from the current domain and can be skipped. This is e.g.
the case in the IPA provider if a POSIX ID used in the IPA domain is
checked in a trusted id-mapped AD domain before the IPA domain is checked.

Resolves https://pagure.io/SSSD/sssd/issue/3452

Additionally this PR adds some missing descriptions for idmap error codes.
"""

To pull the PR as Git branch:
git remote add ghsssd https://github.com/SSSD/sssd
git fetch ghsssd pull/330/head:pr330
git checkout pr330