[SSSD] [sssd PR#128][comment] Fix group renaming issue when "id_provider = ldap" is set

[jhrozek]

URL: https://github.com/SSSD/sssd/pull/128
Title: #128: Fix group renaming issue when "id_provider = ldap" is set

jhrozek commented:
"""
I pushed the patch that detects the group rename vs. GID duplicate to https://github.com/jhrozek/sssd/tree/group_renaming

The rdn_same test now fails when I revert your patches. Thank you for spotting the test was not hitting the codepath at all.

I haven't ran any downstream tests yet, just the integration tests and unit tests. But I would appreciate code review.
"""

See the full comment at https://github.com/SSSD/sssd/pull/128#issuecomment-381725671