remove unusded registrations set from persistence activator

java/com.sap.sailing.domain.persistence/src/com/sap/sailing/domain/persistence/impl/Activator.java

@@ -1,16 +1,11 @@
 package com.sap.sailing.domain.persistence.impl;
 
-import java.util.HashSet;
-import java.util.Set;
-
 import org.osgi.framework.BundleActivator;
 import org.osgi.framework.BundleContext;
-import org.osgi.framework.ServiceRegistration;
 
 import com.sap.sailing.mongodb.MongoDBService;
 
 public class Activator implements BundleActivator {
-    private Set<ServiceRegistration<?>> registrations = new HashSet<>();
     @Override
     public void start(BundleContext context) throws Exception {
         for (CollectionNames name : CollectionNames.values())
@@ -19,10 +14,5 @@ public class Activator implements BundleActivator {
 
     @Override
     public void stop(BundleContext context) throws Exception {
-        for (ServiceRegistration<?> reg : registrations) {
-            reg.unregister();
-        }
-        registrations.clear();
     }
-
 }