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: Ic68a12ef7c12222b1300981282161c971b561dc1
diff --git a/sessions_manager.cpp b/sessions_manager.cpp
index b01ba4a..538aaa4 100644
--- a/sessions_manager.cpp
+++ b/sessions_manager.cpp
@@ -61,7 +61,7 @@
      * through the lifetime of the Session Manager.
      */
 
-    objManager = std::make_unique<sdbusplus::server::manager::manager>(
+    objManager = std::make_unique<sdbusplus::server::manager_t>(
         *getSdBus(), session::sessionManagerRootPath);
 
     auto objPath =