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: Ic63a70d32f4683e0bd92b625cc36c836aa8395a8
diff --git a/test/associations_test.cpp b/test/associations_test.cpp
index 5fa95c3..6515ee3 100644
--- a/test/associations_test.cpp
+++ b/test/associations_test.cpp
@@ -145,7 +145,7 @@
     {}
 
     fs::path jsonDir;
-    sdbusplus::bus::bus bus;
+    sdbusplus::bus_t bus;
 
     virtual void SetUp()
     {