Ensure DNSPython modules are imported correctly

eventlet had previously triggered these imports from their code,
makeing the modules available to us for use.

Now that eventlet no longer does this, we need to explicitly
import the modules we use.

Closes-Bug: 1425616
Change-Id: I104e9eb399c5b3dd100254fc9c68824ba9dd8ec0

designate/agent/handler.py

@@ -14,6 +14,11 @@
 # License for the specific language governing permissions and limitations
 # under the License.
 import dns
+import dns.opcode
+import dns.rcode
+import dns.message
+import dns.flags
+import dns.opcode
 from oslo.config import cfg
 from oslo_log import log as logging
 

designate/mdns/handler.py

@@ -14,6 +14,12 @@
 # License for the specific language governing permissions and limitations
 # under the License.
 import dns
+import dns.flags
+import dns.opcode
+import dns.rcode
+import dns.rdataclass
+import dns.rdatatype
+import dns.message
 from oslo.config import cfg
 from oslo_log import log as logging
 

designate/mdns/notify.py

@@ -15,6 +15,14 @@
 import time
 
 import dns
+import dns.rdataclass
+import dns.rdatatype
+import dns.exception
+import dns.query
+import dns.flags
+import dns.rcode
+import dns.message
+import dns.opcode
 from oslo import messaging
 from oslo.config import cfg
 from oslo_log import log as logging

designate/tests/test_agent/test_handler.py

@@ -16,6 +16,7 @@
 import binascii
 
 import dns
+import dns.resolver
 import mock
 
 import designate

designate/tests/test_mdns/test_notify.py

@@ -15,6 +15,9 @@
 import binascii
 
 import dns
+import dns.message
+import dns.query
+import dns.exception
 from mock import patch
 
 from designate.tests.test_mdns import MdnsTestCase

designate/tests/test_mdns/test_service.py

@@ -17,6 +17,7 @@ import binascii
 import socket
 
 import dns
+import dns.message
 import mock
 
 from designate import dnsutils