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: I9bb7b9a430d029ddaf2a08ea26acb775b9b2b152
diff --git a/test/ca_certs_manager_test.cpp b/test/ca_certs_manager_test.cpp
index fab3c54..3b4e9c5 100644
--- a/test/ca_certs_manager_test.cpp
+++ b/test/ca_certs_manager_test.cpp
@@ -20,7 +20,7 @@
 class MockCACertMgr : public CACertMgr
 {
   public:
-    MockCACertMgr(sdbusplus::bus::bus& bus, const char* path) :
+    MockCACertMgr(sdbusplus::bus_t& bus, const char* path) :
         CACertMgr(bus, path)
     {
     }
@@ -57,7 +57,7 @@
     }
 
   protected:
-    sdbusplus::bus::bus bus;
+    sdbusplus::bus_t bus;
 };
 
 TEST_F(TestCACertMgr, testObjectCreation)