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: I86dfa77a53a306b0e868eeb82de30b270704c455
diff --git a/thresholds.hpp b/thresholds.hpp
index d339ea8..162e1c2 100644
--- a/thresholds.hpp
+++ b/thresholds.hpp
@@ -129,7 +129,7 @@
     auto tHi = env::getEnv(Thresholds<T>::envHi, sensorType, sensorID);
     if (!tLo.empty() || !tHi.empty())
     {
-        auto& bus = *std::get<sdbusplus::bus::bus*>(info);
+        auto& bus = *std::get<sdbusplus::bus_t*>(info);
 
         iface = std::make_shared<T>(bus, objPath.c_str(),
                                     T::action::emit_no_signals);