[OVSDB] Fix ovsdb passive mode connections

Currently ovsdb passive connections are broken. This happens because the
eventloop is never initialized. As a result, in connectRetry() (called
in connect()) the workerGroup is null and the connection to the switch
can't be established.

Change-Id: Ic20a3f699e49f119bd2ba6edb6eb8ad94ba09009
diff --git a/protocols/ovsdb/ctl/src/main/java/org/onosproject/ovsdb/controller/impl/Controller.java b/protocols/ovsdb/ctl/src/main/java/org/onosproject/ovsdb/controller/impl/Controller.java
index 86998c0..c4616be 100644
--- a/protocols/ovsdb/ctl/src/main/java/org/onosproject/ovsdb/controller/impl/Controller.java
+++ b/protocols/ovsdb/ctl/src/main/java/org/onosproject/ovsdb/controller/impl/Controller.java
@@ -254,6 +254,8 @@
                 log.warn("Interrupted while waiting to start");
                 Thread.currentThread().interrupt();
             }
+        } else {
+            initEventLoopGroup();
         }
     }