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
diff --git a/dist/xyz.openbmc_project.Logging.service b/dist/xyz.openbmc_project.Logging.service
index 3a11a96..e988966 100644
--- a/dist/xyz.openbmc_project.Logging.service
+++ b/dist/xyz.openbmc_project.Logging.service
@@ -9,3 +9,4 @@
 
 [Install]
 WantedBy=multi-user.target
+Alias=dbus-xyz.openbmc_project.Logging.service