dbus: add dbus activation support

Add support for dbus activation of phosphor-logging. This will ensure
users of the logging library for calls like "commit" will automatically
have the phosphor-logg

dbus: add dbus activation support

Add support for dbus activation of phosphor-logging. This will ensure
users of the logging library for calls like "commit" will automatically
have the phosphor-logging service start (if not already running) and not
need to put this dependency in their service files.

Tested:
- Stopped xyz.openbmc_project.Logging.service and then used busctl to
create an error log. Verified that xyz.openbmc_project.Logging.service
was automatically started and the error was created.

Signed-off-by: Andrew Geissler <geissonator@yahoo.com>
Change-Id: I9134851c075dbb717f832422f55e2eeee31f823b

show more ...