[SSSD] [sssd PR#509][opened] SPEC: Fix systemd executions/requirements

[lslebodn]

   URL: https://github.com/SSSD/sssd/pull/509
Author: lslebodn
 Title: #509: SPEC: Fix systemd executions/requirements
Action: opened

PR body:
"""
The rpm macro systemd_requires is even in el7 and using this macro
nicer then using different requires (systemd-units vs systemd)
There is a plan to remove provides for systemd-units from rawhide.

systemd was added to BuildRequires because it provides rpm macros
/usr/lib/rpm/macros.d/macros.systemd and it is unreliable to rely
on indirect dependency between systemd-devel and systemd

  sh$ rpm --eval "%{?systemd_requires}"

  Requires(post): systemd
  Requires(preun): systemd
  Requires(postun): systemd

  sh$ rpm -q --whatprovides systemd-units
  systemd-237-1.fc28.x86_64

  sh$ rpm -qf /usr/lib/rpm/macros.d/macros.systemd
  systemd-237-1.fc28.x86_64
"""

To pull the PR as Git branch:
git remote add ghsssd https://github.com/SSSD/sssd
git fetch ghsssd pull/509/head:pr509
git checkout pr509