Service broker considered available if state is empty

for compatibility with v2

[#172976573](https://www.pivotaltracker.com/story/show/172976573)

Author: pivotal-marcela-campo

app/models/services/service_broker.rb

@@ -39,7 +39,7 @@ def in_transitional_state?
     end
 
     def available?
-      self.state == ServiceBrokerStateEnum::AVAILABLE
+      self.state.blank? || self.state == ServiceBrokerStateEnum::AVAILABLE
     end
 
     def space_scoped?

spec/request/service_instances_spec.rb

@@ -931,6 +931,16 @@ def check_filtered_instances(*instances)
         end
       end
 
+      context 'when the service broker does not have state (v2 brokers)' do
+        let(:service_broker) { service_plan.service_broker }
+
+        it 'creates a service instance' do
+          service_broker.update(state: '')
+          api_call.call(space_dev_headers)
+          expect(last_response).to have_status_code(202)
+        end
+      end
+
       context 'when there is an operation in progress for the service broker' do
         let(:service_broker) { service_plan.service_broker }
 

spec/unit/models/services/service_broker_spec.rb

@@ -108,6 +108,10 @@ module VCAP::CloudController
         broker.state = ServiceBrokerStateEnum::AVAILABLE
         expect(broker.available?).to eq true
       end
+      it 'returns true when state is empty to support old brokers' do
+        broker.state = ''
+        expect(broker.available?).to eq true
+      end
       it 'returns false when state is DELETE_IN_PROGRESS' do
         broker.state = ServiceBrokerStateEnum::DELETE_IN_PROGRESS
         expect(broker.available?).to eq false