entity-manager: size_t propertiesChangedInstance

Move
```
static size_t instance = 0;
```
into EM class as
```
size_t propertiesChangedInstance = 0;
```
to get rid of the static variable.

Tested: On Tyan S8030. propertiesChangedCallback is still called.

Change-Id: I8bb283feee6f1857ed32a61715d6868620b3a1a2
Signed-off-by: Alexander Hansen <alexander.hansen@9elements.com>
diff --git a/src/entity_manager/entity_manager.cpp b/src/entity_manager/entity_manager.cpp
index ba2af63..8de134a 100644
--- a/src/entity_manager/entity_manager.cpp
+++ b/src/entity_manager/entity_manager.cpp
@@ -467,9 +467,8 @@
 // main properties changed entry
 void EntityManager::propertiesChangedCallback()
 {
-    static size_t instance = 0;
-    instance++;
-    size_t count = instance;
+    propertiesChangedInstance++;
+    size_t count = propertiesChangedInstance;
 
     propertiesChangedTimer.expires_after(std::chrono::milliseconds(500));
 
@@ -532,7 +531,7 @@
 
                     boost::asio::post(io, [this, newConfiguration, count] {
                         publishNewConfiguration(
-                            std::ref(instance), count,
+                            std::ref(propertiesChangedInstance), count,
                             std::ref(propertiesChangedTimer), newConfiguration);
                     });
                 });