javadoc fixes

Change-Id: I3b4fc2d99f42b2413a535fb411b9c19bdd186ad8
diff --git a/core/api/src/main/java/org/onlab/onos/net/device/DeviceStore.java b/core/api/src/main/java/org/onlab/onos/net/device/DeviceStore.java
index f3f124a..bc0b5c1 100644
--- a/core/api/src/main/java/org/onlab/onos/net/device/DeviceStore.java
+++ b/core/api/src/main/java/org/onlab/onos/net/device/DeviceStore.java
@@ -125,6 +125,7 @@
      * Administratively removes the specified device from the store.
      *
      * @param deviceId device to be removed
+     * @return null if no such device, or was forwarded to remove master
      */
     DeviceEvent removeDevice(DeviceId deviceId);
 }