Adding some tests for GossipDeviceStore + bugfix

Change-Id: Ic0d55fa499b1d66131f059b4a47cd105c55a6e63
diff --git a/core/store/dist/pom.xml b/core/store/dist/pom.xml
index 7b00833..33517c7 100644
--- a/core/store/dist/pom.xml
+++ b/core/store/dist/pom.xml
@@ -62,6 +62,11 @@
             <groupId>org.apache.commons</groupId>
             <artifactId>commons-lang3</artifactId>
         </dependency>
+        <dependency>
+          <groupId>org.easymock</groupId>
+          <artifactId>easymock</artifactId>
+          <scope>test</scope>
+        </dependency>
     </dependencies>
 
     <build>