(PUP-3228) Remove "{}" from PUPPETMASTER_EXTRA_OPTS and
PUPPET_EXTRA_OPTS in systemd files

The "{}" prevent systemd from interpreting values correctly and causes
services to fail to start
Merge pull request #3015 from tmclaugh/systemd_sysconfig_vars

(PUP-3228) Remove "{}" from PUPPETMASTER_EXTRA_OPTS and PUPPET_EXTRA_OPTS