(maint) Update rpm spec to support systemd in el/fedora and suse
(maint) Update rpm spec and systemd service file for pidfile handling

Previously, the rpm package was creating /var/run/puppetdb at install time for
pidfile storage. This will break on modern Fedora/RHEL and SUSE systems as
/var/run (which is a symlink to /run) uses tmpfs and will not persist through a
reboot.

As the systemd service type is "simple", meaning non-forking, systemd
manages the process directly, and the PIDfile is not needed or used on
those platforms.
(maint) Update "sles-release" dependency to "distribution-release" virtual package

The "sles-release" package only exists SLES. distribution-release
is a virtual package that will install sles-release on SLES, or
OpenSUSE-release on OpenSUSE.
Merge pull request #1072 from shrug/maint/master/systemd

(maint)(packaging) Updates to packaging for improved systemd support and PID dir handling