Use consul_kv_fail instead of consul_kv_blocker

Blocker blocks all puppet execution once it is executed (not only dependant resources)
until the dependancy available. So better just fail all dependant resources
rather than blocks unncessary resources.

As a POC, just using fail for neutron floating IP before creating contrail vgw.
Merge pull request #237 from hkumarmk/consul_kv_fail

Use consul_kv_fail instead of consul_kv_blocker