[SSSD] [sssd PR#563][opened] SYSDB: Only check non-POSIX groups for GID conflicts

[jhrozek]

   URL: https://github.com/SSSD/sssd/pull/563
Author: jhrozek
 Title: #563: SYSDB: Only check non-POSIX groups for GID conflicts
Action: opened

PR body:
"""
When checking for a GID conflict, it doesn't make sense to check for one
when the group being added is a non-POSIX one, because then the GID will
always be 0.
"""

To pull the PR as Git branch:
git remote add ghsssd https://github.com/SSSD/sssd
git fetch ghsssd pull/563/head:pr563
git checkout pr563