[SSSD] [sssd PR#809][synchronized] sss_cache: Do nothing if SYSTEMD_OFFLINE=1

[thalman]

   URL: https://github.com/SSSD/sssd/pull/809
Author: thalman
 Title: #809: sss_cache: Do nothing if SYSTEMD_OFFLINE=1
Action: synchronized

To pull the PR as Git branch:
git remote add ghsssd https://github.com/SSSD/sssd
git fetch ghsssd pull/809/head:pr809
git checkout pr809