CORD-73 Change the way we configure host learning in segment routing

hostLearning config
    - true: enable host learning
    - false or not provided: disable host learning
suppressHost config
    - all connect points listed here will be ignored
    - no effect if hostLearning is false
    - accept all hosts if this config is not provided

Change-Id: Id4a60bd47cac1f226ab8ba5391931ad2fb798529
diff --git a/apps/segmentrouting/BUCK b/apps/segmentrouting/BUCK
index f532bea..7cb8d69 100644
--- a/apps/segmentrouting/BUCK
+++ b/apps/segmentrouting/BUCK
@@ -5,6 +5,7 @@
     '//cli:onos-cli',
     '//core/store/serializers:onos-core-serializers',
     '//incubator/api:onos-incubator-api',
+    '//providers/netcfghost:onos-providers-netcfghost',
     '//utils/rest:onlab-rest',
 ]