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

Change-Id: I14b39033b24fd43d85e3f3cb83ac38ea57a4884a
Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
diff --git a/utils.hpp b/utils.hpp
index cbb7248..febcb6a 100644
--- a/utils.hpp
+++ b/utils.hpp
@@ -18,7 +18,7 @@
  *
  * @return void, will throw exception on failure
  */
-void subscribeToSystemdSignals(sdbusplus::bus::bus& bus);
+void subscribeToSystemdSignals(sdbusplus::bus_t& bus);
 
 /** @brief Get service name from object path and interface
  *