entity-manager: propertiesChangedTimer

Move the
```
static boost::asio::steady_timer timer(io);
```
into EM class as
```
boost::asio::steady_timer propertiesChangedTimer;
```
to get rid of the static variable.

Renaming the timer causes a diff in the lambda in
propertiesChangedCallback, but otherwise the lambda is unchanged.
The diff is only due to formatting.

Tested: On Tyan S8030

Did a host powercycle via ```ipmitool power cycle```
and the callback is still run.

Change-Id: Iabc8057f8e0c326c6f64e798a7bfb6f68dfefccd
Signed-off-by: Alexander Hansen <alexander.hansen@9elements.com>
diff --git a/src/entity_manager/entity_manager.hpp b/src/entity_manager/entity_manager.hpp
index f730dde..5b5bbf6 100644
--- a/src/entity_manager/entity_manager.hpp
+++ b/src/entity_manager/entity_manager.hpp
@@ -69,6 +69,7 @@
     bool scannedPowerOn = false;
 
     bool propertiesChangedInProgress = false;
+    boost::asio::steady_timer propertiesChangedTimer;
 
     void startRemovedTimer(boost::asio::steady_timer& timer,
                            nlohmann::json& systemConfiguration);