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: I96286490697ce5d7fecc1c9c358f5f1d054137ec
diff --git a/image_manager.cpp b/image_manager.cpp
index b02abd3..eb4fec4 100644
--- a/image_manager.cpp
+++ b/image_manager.cpp
@@ -59,7 +59,7 @@
 namespace // anonymous
 {
 
-std::vector<std::string> getSoftwareObjects(sdbusplus::bus::bus& bus)
+std::vector<std::string> getSoftwareObjects(sdbusplus::bus_t& bus)
 {
     std::vector<std::string> paths;
     auto method = bus.new_method_call(MAPPER_BUSNAME, MAPPER_PATH,