provider/neutron.rb: fix list_router_ports

The json output of neutron router-interface-list may contain an
an empty 'fixed_ips' field for a port, but JSON.parse does not
work with empty strings. A check is added to ensure that empty
'fixed_ips' fields are directly removed.

Change-Id: Ie130e1c0b9b8fbbfc679ce0c8b5320226249617f

lib/puppet/provider/neutron.rb

@@ -210,8 +210,10 @@ correctly configured.")
 
     self.find_and_parse_json(cmd_output).each do |port|
       if port['fixed_ips']
+        if !port['fixed_ips'].empty?
           fixed_ips = JSON.parse(port['fixed_ips'])
           port['subnet_id'] = fixed_ips['subnet_id']
+        end
         port.delete('fixed_ips')
       end
       results << port

spec/unit/provider/neutron_spec.rb

@@ -243,6 +243,29 @@ describe Puppet::Provider::Neutron do
       expect(result).to eql(expected)
     end
 
+
+    it 'should handle empty fixed_ips field' do
+      output = '''
+        [
+            {
+                "id": "1345e576-a21f-4c2e-b24a-b245639852ab",
+                "name": "",
+                "mac_address": "fa:16:3e:e3:e6:38",
+                "fixed_ips": ""
+            }
+        ]
+      '''
+      expected =
+       [{ "name"=>"",
+          "id"=>"1345e576-a21f-4c2e-b24a-b245639852ab",
+          "mac_address"=>"fa:16:3e:e3:e6:38"}]
+      klass.expects(:auth_neutron).
+        with('router-port-list', '--format=json', router).
+        returns(output)
+      result = klass.list_router_ports(router)
+      expect(result).to eql(expected)
+    end
+
   end
 
   describe 'when parsing creation output' do