Avoid duplicate unregistration

git-svn-id: https://svn.apache.org/repos/asf/felix/trunk@1660921 13f79535-47bb-0310-9956-ffa450edef68
diff --git a/http/base/src/main/java/org/apache/felix/http/base/internal/console/HttpServicePlugin.java b/http/base/src/main/java/org/apache/felix/http/base/internal/console/HttpServicePlugin.java
index fe30a54..8665277 100644
--- a/http/base/src/main/java/org/apache/felix/http/base/internal/console/HttpServicePlugin.java
+++ b/http/base/src/main/java/org/apache/felix/http/base/internal/console/HttpServicePlugin.java
@@ -189,6 +189,7 @@
         if (this.serviceReg != null)
         {
             this.serviceReg.unregister();
+            this.serviceReg = null;
         }
     }