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: Ibc25db433a6926f7ee43ea83312c3ac14f480c33
diff --git a/test/openpower-pels/pel_manager_test.cpp b/test/openpower-pels/pel_manager_test.cpp
index 41d6138..fc77a5e 100644
--- a/test/openpower-pels/pel_manager_test.cpp
+++ b/test/openpower-pels/pel_manager_test.cpp
@@ -63,7 +63,7 @@
     }
 
     NiceMock<sdbusplus::SdBusMock> sdbusInterface;
-    sdbusplus::bus::bus bus;
+    sdbusplus::bus_t bus;
     phosphor::logging::internal::Manager logManager;
     sd_event* sdEvent;
     TestLogger logger;