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: Ie0805a98908ddca5c97471588adc160d9f5633c6
Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
diff --git a/health_metric.hpp b/health_metric.hpp
index e0c75f9..01f6836 100644
--- a/health_metric.hpp
+++ b/health_metric.hpp
@@ -42,7 +42,7 @@
     HealthMetric(HealthMetric&&) = delete;
     virtual ~HealthMetric() = default;
 
-    HealthMetric(sdbusplus::bus::bus& bus, phosphor::health::metric::Type type,
+    HealthMetric(sdbusplus::bus_t& bus, phosphor::health::metric::Type type,
                  const config::HealthMetric& config, const paths_t& bmcPaths) :
         MetricIntf(bus, getPath(config.subType).c_str(), action::defer_emit),
         bus(bus), type(type), config(config)
@@ -67,7 +67,7 @@
     /** @brief Get the object path for the given subtype */
     auto getPath(SubType subType) -> std::string;
     /** @brief D-Bus bus connection */
-    sdbusplus::bus::bus& bus;
+    sdbusplus::bus_t& bus;
     /** @brief Metric type */
     phosphor::health::metric::Type type;
     /** @brief Metric configuration */