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/fan.cpp b/control/json/fan.cpp
index edd8514..673859a 100644
--- a/control/json/fan.cpp
+++ b/control/json/fan.cpp
@@ -32,8 +32,8 @@
 constexpr auto FAN_SENSOR_PATH = "/xyz/openbmc_project/sensors/fan_tach/";
 constexpr auto FAN_TARGET_PROPERTY = "Target";
 
-Fan::Fan(const json& jsonObj, sdbusplus::bus::bus& bus) :
-    ConfigBase(jsonObj), _bus(bus)
+Fan::Fan(const json& jsonObj) :
+    ConfigBase(jsonObj), _bus(util::SDBusPlus::getBus())
 {
     setInterface(jsonObj);
     setSensors(jsonObj);