v3(services): broker client to follow redirects (cloudfoundry#1896)

See: cloudfoundry#1893

[#175213685](https://www.pivotaltracker.com/story/show/175213685)

Author: Derik Evangelista

lib/services/service_brokers/v2/http_client.rb

@@ -48,15 +48,15 @@ def uri_for(path)
 
       def make_request(method, uri, body=nil, options={})
         client = HTTPClient.new(force_basic_auth: true)
-        client.set_auth(uri, auth_username, auth_password)
+        client.set_auth(nil, auth_username, auth_password)
         client.ssl_config.set_default_paths
 
         client.ssl_config.verify_mode = verify_certs? ? OpenSSL::SSL::VERIFY_PEER : OpenSSL::SSL::VERIFY_NONE
         client.connect_timeout = broker_client_timeout
         client.receive_timeout = broker_client_timeout
         client.send_timeout = broker_client_timeout
 
-        opts = { body: body, header: {} }
+        opts = { body: body, header: {}, follow_redirect: true }
 
         client.default_header = default_headers
         opts[:header]['Content-Type'] = options[:content_type] if options[:content_type]

spec/unit/lib/services/service_brokers/v2/http_client_spec.rb

@@ -311,6 +311,26 @@ def expect_timeout_to_be(timeout)
       end
     end
 
+    shared_examples 'client that follows redirects' do
+      let(:another_url) { "http://another-broker.example.com#{path}" }
+
+      before do
+        stub_request(http_method, full_url).
+          with(basic_auth: basic_auth).
+          to_return(status: 301, body: {}.to_json, headers: { Location: another_url })
+
+        stub_request(http_method, another_url).
+          with(basic_auth: basic_auth).
+          to_return(status: 200, body: '')
+      end
+
+      it 'should follow redirects' do
+        request
+
+        expect(a_request(http_method, another_url)).to have_been_made
+      end
+    end
+
     describe '#get' do
       let(:http_method) { :get }
 
@@ -368,6 +388,10 @@ def expect_timeout_to_be(timeout)
       it_behaves_like 'client that maps status codes to status code messages' do
         let(:request) { client.get(path) }
       end
+
+      it_behaves_like 'client that follows redirects' do
+        let(:request) { client.get(path) }
+      end
     end
 
     describe '#put' do