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/tools/package/config/samples/network-cfg-fabric-2x2-all.json b/tools/package/config/samples/network-cfg-fabric-2x2-all.json
index b12d4dc..499d763 100644
--- a/tools/package/config/samples/network-cfg-fabric-2x2-all.json
+++ b/tools/package/config/samples/network-cfg-fabric-2x2-all.json
@@ -234,6 +234,7 @@
                 "suppressSubnet" : [
                     "of:0000000000000002/31", "of:0000000000000002/32"
                 ],
+                "hostLearning" : true,
                 "suppressHost" : [
                     "of:0000000000000001/65", "of:0000000000000001/73",
                     "of:0000000000000002/31", "of:0000000000000002/32"