(PDB-468) Update scripts to use correct JAVA_BIN

The systemd service file and some of the other utility scripts were
using a hard-coded path to /usr/bin/java, instead of the java path
set in the system defaults file.

This commit updates those scripts to source the defaults file where
available, and fall back to sane defaults otherwise.
(PDB-468) Break out script common environment to LIBEXECDIR
(PDB-468) Update el spec file for added environment file
(PDB-142) Update puppetdb-foreground to respect JAVA_ARGS
(PDB-468) Change back to default java_args in non-persistent scripts
Merge pull request #864 from shrug/bug/pdb-468/1.6.x

(PDB-468) Update scripts to use correct JAVA_BIN
(pdb-468)(packaging) Fix package build on systemd platforms

The previous commit added the defaults file to /etc/sysconfig for
Fedora 19 or Fedora 20, but neglected to create the /etc/sysconfig
directory in the RPM buildroot.

This commit creates the proper directory in the buildroot for builds
on Fedora >= 19 and EL >=7 (systemd platforms)
Merge pull request #866 from shrug/1.6.x

(pdb-468)(packaging) Fix package build on systemd platforms
Merge remote-tracking branch 'upstream/1.6.x'

* upstream/1.6.x:
  (pdb-468)(packaging) Fix package build on systemd platforms
  (PDB-468) Change back to default java_args in non-persistent scripts
  (PDB-142) Update puppetdb-foreground to respect JAVA_ARGS
  (PDB-468) Update el spec file for added environment file
  (PDB-468) Break out script common environment to LIBEXECDIR
  (PDB-468) Update scripts to use correct JAVA_BIN