systemd.bbclass: make easier handle service enabling
systemd.bbclass: make easier handle service enabling

This generates the postinst/prerm/postrm routines for the package
specified in SYSTEMD_PACKAGES avoding code duplication and
centralizing the handling of it for easy maintainence work.

Signed-off-by: Otavio Salvador <1d31b11c1b92bf5d043d36edfe7174db39a6b891@ossystems.com.br>
Signed-off-by: Koen Kooi <42e3d96910f922bdd7dd1805fe3f8aff634f391d@dominion.thruhere.net>

WindRiver-OpenSourceLabs/meta-oe-subset,WindRiver-OpenSourceLabs/meta-oe-subset