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: I2d7ce287e0adc0be60796a80e9bb4cca908434ce
diff --git a/nvme_manager.hpp b/nvme_manager.hpp
index 391a768..0ee23df 100644
--- a/nvme_manager.hpp
+++ b/nvme_manager.hpp
@@ -35,7 +35,7 @@
      * @param[in] bus     - Handle to system dbus
      * @param[in] objPath - The dbus path of nvme
      */
-    Nvme(sdbusplus::bus::bus& bus) :
+    Nvme(sdbusplus::bus_t& bus) :
         bus(bus), _event(sdeventplus::Event::get_default()),
         _timer(_event, std::bind(&Nvme::read, this))
     {
@@ -134,7 +134,7 @@
 
   private:
     /** @brief sdbusplus bus client connection. */
-    sdbusplus::bus::bus& bus;
+    sdbusplus::bus_t& bus;
     /** @brief the Event Loop structure */
     sdeventplus::Event _event;
     /** @brief Read Timer */