Title: #166: Please see the commit message for commit description.
To reproduce, log in as a user from a trusted domain. Before the patch,
you should see an error message about the domain not being found such as:
(Wed Feb 22 20:35:33 2017) [sssd[nss]] [nss_update_initgr_memcache] (0x0040): Unknown
domain (win.trust.test) requested by provider
and the memory cache wouldn't be in fact be invalidated.
To pull the PR as Git branch:
git remote add ghsssd https://github.com/SSSD/sssd
git fetch ghsssd pull/166/head:pr166
git checkout pr166