Reworked the dependency on default drivers. Driver manager must NOT depend on these.
Instead, it is ok for the flow manager to have a dependency on the drivers and go fully active/dormant when the default drivers arrive/depart.
Removed inclusion of the onos-drivers bundle as part of the onos-openflow app as this caused an unwanted dependency.

Change-Id: I614290277d1621c8243c0c19e5d79273f2168016
diff --git a/core/api/src/main/java/org/onosproject/net/driver/DefaultDriverProviderService.java b/core/api/src/main/java/org/onosproject/net/driver/DefaultDriverProviderService.java
index 2b7eeff..153c7c5 100644
--- a/core/api/src/main/java/org/onosproject/net/driver/DefaultDriverProviderService.java
+++ b/core/api/src/main/java/org/onosproject/net/driver/DefaultDriverProviderService.java
@@ -17,7 +17,7 @@
 package org.onosproject.net.driver;
 
 /**
- * Service capable of providing a set of default drivers.
+ * Service representing availability of default drivers.
  */
-public interface DefaultDriverProviderService extends DriverProvider {
+public interface DefaultDriverProviderService {
 }