control: Switch to using static instance of bus

Update main to use the static reference of the bus from
util::SDBusPlus.getBus() and have each object that needs the bus call
that same util::SDBusPlus.getBus() function to retrieve the same static
reference.

Change-Id: Icd5a0e61819bf1bec8b46daae05443fdcc542b05
Signed-off-by: Matthew Barth <msbarth@us.ibm.com>
diff --git a/control/json/zone.hpp b/control/json/zone.hpp
index d9d6815..670781b 100644
--- a/control/json/zone.hpp
+++ b/control/json/zone.hpp
@@ -78,12 +78,10 @@
      * Parses and populates a zone from JSON object data
      *
      * @param[in] jsonObj - JSON object
-     * @param[in] bus - sdbusplus bus object
      * @param[in] event - sdeventplus event loop
      * @param[in] mgr - Manager of this zone
      */
-    Zone(const json& jsonObj, sdbusplus::bus::bus& bus,
-         const sdeventplus::Event& event, Manager* mgr);
+    Zone(const json& jsonObj, const sdeventplus::Event& event, Manager* mgr);
 
     /**
      * @brief Get the default ceiling