Use unique_ptr for sd_event object wrapper

Convert the sd_event object wrapper from a shared_ptr to
a unique_ptr.  Requires a new header file.

Change-Id: I868a9e88ed93878c2e0bb12e58f8d3a604510da0
Signed-off-by: Matt Spinler <spinler@us.ibm.com>
diff --git a/monitor/fan.hpp b/monitor/fan.hpp
index 910b4eb..8e7f86f 100644
--- a/monitor/fan.hpp
+++ b/monitor/fan.hpp
@@ -3,6 +3,7 @@
 #include <sdbusplus/bus.hpp>
 #include <tuple>
 #include <vector>
+#include "event.hpp"
 #include "tach_sensor.hpp"
 #include "types.hpp"
 
@@ -72,7 +73,7 @@
          * @param def - the fan definition structure
          */
         Fan(sdbusplus::bus::bus& bus,
-            std::shared_ptr<sd_event>& events,
+            phosphor::fan::event::EventPtr& events,
             const FanDefinition& def);
 
         /**