sdbusplus: use shorter type aliases

The sdbusplus headers provide shortened aliases for many types.
Switch to using them to provide better code clarity and shorter
lines.  Possible replacements are for:
  * bus_t
  * exception_t
  * manager_t
  * match_t
  * message_t
  * object_t
  * slot_t

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: Ie36d234f4580029a7832a0cd179f3bb78a1a403f
diff --git a/test/helpers.hpp b/test/helpers.hpp
index 1b5486e..1f41523 100644
--- a/test/helpers.hpp
+++ b/test/helpers.hpp
@@ -31,7 +31,7 @@
  * TODO: Make it support more cases, as I'm sure there are more.
  *
  * @param[in] sdbus_mock - Pointer to your sdbus mock interface used with
- *     the sdbusplus::bus::bus you created.
+ *     the sdbusplus::bus_t you created.
  * @param[in] defer - Whether object announcement is deferred.
  * @param[in] path - the dbus path passed to the object
  * @param[in] intf - the dbus interface