Option expose IP instead of dnshost in ec2 desc'

As documented in bug 901594, previous nova releases, the IP address
was exposed as the DNS hostname, which worked well with euca-tools.
This is unfortunately not always ideal for private clouds.

Whilst it is expected to be able to euca-describe-instances --ipv4
in newer euca2ools releases, this behaviour is not always desired.

This patchset allows the nova admin to set a global flag of:
--ec2_private_dns_show_ip=True, to restore legacy nova behaviour.

This does not change the current default behaviour of nova.

Change-Id: I7c71ffe63929d90d45d9c724ab3409dcdee52b44

.mailmap

@@ -18,6 +18,7 @@
 <corywright@gmail.com> <cory.wright@rackspace.com>
 <dan@nicira.com> <danwent@dan-xs3-cs>
 <dan@nicira.com> <danwent@gmail.com>
+<Dave.Walker@canonical.com> <DaveWalker@ubuntu.com>
 <derekh@redhat.com> <higginsd@gmail.com>
 <devin.carlen@gmail.com> <devcamcar@illian.local>
 <dprince@redhat.com> <dan.prince@rackspace.com>

Authors

@@ -40,7 +40,7 @@ Dan Prince <dprince@redhat.com>
 Dan Wendlandt <dan@nicira.com>
 Daniel P. Berrange <berrange@redhat.com>
 Dave Lapsley <dlapsley@nicira.com>
-Dave Walker <DaveWalker@ubuntu.com>
+Dave Walker <Dave.Walker@canonical.com>
 David Pravec <David.Pravec@danix.org>
 David Subiros <david.perez5@hp.com>
 Dean Troyer <dtroyer@gmail.com>

nova/api/ec2/__init__.py

@@ -56,6 +56,10 @@ ec2_opts = [
     cfg.StrOpt('keystone_ec2_url',
                default='http://localhost:5000/v2.0/ec2tokens',
                help='URL to get token from ec2 request.'),
+    cfg.BoolOpt('ec2_private_dns_show_ip',
+                default=False,
+                help='Return the IP address as private dns hostname in '
+                     'describe instances'),
     ]
 
 FLAGS = flags.FLAGS

nova/api/ec2/cloud.py

@@ -1148,7 +1148,10 @@ class CloudController(object):
                 floating_ip = ip_info['floating_ips'][0]
             if ip_info['fixed_ip6s']:
                 i['dnsNameV6'] = ip_info['fixed_ip6s'][0]
-            i['privateDnsName'] = instance['hostname']
+            if FLAGS.ec2_private_dns_show_ip:
+                i['privateDnsName'] = fixed_ip
+            else:
+                i['privateDnsName'] = instance['hostname']
             i['privateIpAddress'] = fixed_ip
             i['publicDnsName'] = floating_ip
             i['ipAddress'] = floating_ip or fixed_ip