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

Change-Id: I2d75afd5b8786a82fccb9d2e06e0696005b8e839
Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
diff --git a/thresholds.hpp b/thresholds.hpp
index 63e1884..1860d7c 100644
--- a/thresholds.hpp
+++ b/thresholds.hpp
@@ -54,7 +54,7 @@
     static constexpr auto name = "Warning";
     using WarningObject::WarningObject;
     /** @brief sdbusplus bus client connection. */
-    sdbusplus::bus::bus& bus;
+    sdbusplus::bus_t& bus;
     std::string objPath;
 
     /** @brief Virtual sensor path/interface in entityManagerDbus.
@@ -68,7 +68,7 @@
      *  @param[in] bus - Bus to attach to.
      *  @param[in] path - Path to attach at.
      */
-    Threshold(sdbusplus::bus::bus& bus, const char* path) :
+    Threshold(sdbusplus::bus_t& bus, const char* path) :
         WarningObject(bus, path), bus(bus), objPath(std::string(path))
     {}
 
@@ -165,7 +165,7 @@
     static constexpr auto name = "Critical";
 
     /** @brief sdbusplus bus client connection. */
-    sdbusplus::bus::bus& bus;
+    sdbusplus::bus_t& bus;
     std::string objPath;
 
     /** @brief Virtual sensor path/interface in entityManagerDbus.
@@ -181,7 +181,7 @@
      *  @param[in] bus - Bus to attach to.
      *  @param[in] path - Path to attach at.
      */
-    Threshold(sdbusplus::bus::bus& bus, const char* path) :
+    Threshold(sdbusplus::bus_t& bus, const char* path) :
         CriticalObject(bus, path), bus(bus), objPath(std::string(path))
     {}