Title: #624: Fix "test-find-uid" and "find_uid-tests" tests
Handle a "hidepid=1" mount option for procfs. One of the affects - this
option makes impermissible non own pid subdirectories on /proc.
To pull the PR as Git branch:
git remote add ghsssd https://github.com/SSSD/sssd
git fetch ghsssd pull/624/head:pr624
git checkout pr624