Switch to using svc-map element for systemd based agent.
This allows both .deb and .rpm installs to share the
element for systemd based installs. There are not any
plans to package a .rpm package for upstart or sysv, so
these are left as is.
Change-Id: Idca7ad97355cae785162989774a7e6dea6fdc5b5
Closes-Bug: #1490584
