Update Gandi tests and fixtures for NULL SRV records

Thanks to @yzguy for assisting with API tests to confirm support

tests/fixtures/gandi-no-changes.json

@@ -123,6 +123,24 @@
           "2.2.3.6"
         ]
       },
+      {
+        "rrset_type": "SRV",
+        "rrset_ttl": 600,
+        "rrset_name": "_imap._tcp",
+        "rrset_href": "https://api.gandi.net/v5/livedns/domains/unit.tests/records/_imap._tcp/SRV",
+        "rrset_values": [
+          "0 0 0 ."
+        ]
+      },
+      {
+        "rrset_type": "SRV",
+        "rrset_ttl": 600,
+        "rrset_name": "_pop3._tcp",
+        "rrset_href": "https://api.gandi.net/v5/livedns/domains/unit.tests/records/_pop3._tcp/SRV",
+        "rrset_values": [
+          "0 0 0 ."
+        ]
+      },
       {
         "rrset_type": "SRV",
         "rrset_ttl": 600,

tests/test_octodns_provider_gandi.py

@@ -117,7 +117,7 @@ class TestGandiProvider(TestCase):
 
             zone = Zone('unit.tests.', [])
             provider.populate(zone)
-            self.assertEquals(14, len(zone.records))
+            self.assertEquals(16, len(zone.records))
             changes = self.expected.changes(zone, provider)
             self.assertEquals(0, len(changes))
 
@@ -284,6 +284,22 @@ class TestGandiProvider(TestCase):
                     '12 20 30 foo-2.unit.tests.'
                 ]
             }),
+            call('POST', '/livedns/domains/unit.tests/records', data={
+                'rrset_name': '_pop3._tcp',
+                'rrset_ttl': 600,
+                'rrset_type': 'SRV',
+                'rrset_values': [
+                    '0 0 0 .',
+                ]
+            }),
+            call('POST', '/livedns/domains/unit.tests/records', data={
+                'rrset_name': '_imap._tcp',
+                'rrset_ttl': 600,
+                'rrset_type': 'SRV',
+                'rrset_values': [
+                    '0 0 0 .',
+                ]
+            }),
             call('POST', '/livedns/domains/unit.tests/records', data={
                 'rrset_name': '@',
                 'rrset_ttl': 3600,
@@ -307,7 +323,7 @@ class TestGandiProvider(TestCase):
             })
         ])
         # expected number of total calls
-        self.assertEquals(17, provider._client._request.call_count)
+        self.assertEquals(19, provider._client._request.call_count)
 
         provider._client._request.reset_mock()