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: I17807e986cefa6a3d9e757c533ac373035438aed
diff --git a/test/external_storer_file_test.cpp b/test/external_storer_file_test.cpp
index f2718aa..04f6b2b 100644
--- a/test/external_storer_file_test.cpp
+++ b/test/external_storer_file_test.cpp
@@ -53,7 +53,7 @@
 
   protected:
     sdbusplus::SdBusMock sdbusMock;
-    sdbusplus::bus::bus bus;
+    sdbusplus::bus_t bus;
     std::unique_ptr<FileHandlerInterface> mockFileWriter;
     std::unique_ptr<ExternalStorerFileInterface> exStorer;
     MockFileWriter* mockFileWriterPtr;