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: I19e094a2a99893627dbb82b615f630b87ad90fdd
diff --git a/users.cpp b/users.cpp
index 239459a..8906769 100644
--- a/users.cpp
+++ b/users.cpp
@@ -58,7 +58,7 @@
  *  @param[in] enabled - user enabled state
  *  @param[in] parent - user manager - parent object
  */
-Users::Users(sdbusplus::bus::bus& bus, const char* path,
+Users::Users(sdbusplus::bus_t& bus, const char* path,
              std::vector<std::string> groups, std::string priv, bool enabled,
              UserMgr& parent) :
     Interfaces(bus, path, Interfaces::action::defer_emit),