Bring back Python 2.6 compat (don"t use dict comprehension)

We have a couple of places where we use dict comprehension. Dict
comprehension are just syntaxic sugar and can be replaced with
dict((k,v) for k,v in iterable) for Python 2.6 compat

I know Tempest doesn"t support Python 2.6 anymore and I agree it's
the good decision. But I am not a fan of "dropping support for the
sake of it", without compeling reason (like using a new module).

I am in charge of a 3rd party CI and my employer wants to have
Centos 6 support for OpenStack Juno. We use Tempest as our non-reg
test suite. Tempest is branchless.

This patch brings back Python 2.6 compatibility.

Change-Id: I23aeafcc9e68d09342a773d2e202f01884080fa3
diff --git a/tempest/api/network/test_dhcp_ipv6.py b/tempest/api/network/test_dhcp_ipv6.py
index f362f85..f8c64ed 100644
--- a/tempest/api/network/test_dhcp_ipv6.py
+++ b/tempest/api/network/test_dhcp_ipv6.py
@@ -128,7 +128,7 @@
         ):
             kwargs = {'ipv6_ra_mode': ra_mode,
                       'ipv6_address_mode': add_mode}
-            kwargs = {k: v for k, v in six.iteritems(kwargs) if v}
+            kwargs = dict((k, v) for k, v in six.iteritems(kwargs) if v)
             real_ip, eui_ip = self._get_ips_from_subnet(**kwargs)
             self._clean_network()
             self.assertEqual(eui_ip, real_ip,
@@ -275,7 +275,7 @@
         ):
             kwargs = {'ipv6_ra_mode': ra_mode,
                       'ipv6_address_mode': add_mode}
-            kwargs = {k: v for k, v in six.iteritems(kwargs) if v}
+            kwargs = dict((k, v) for k, v in six.iteritems(kwargs) if v)
             subnet = self.create_subnet(self.network, **kwargs)
             port = self.create_port(self.network)
             port_ip = next(iter(port['fixed_ips']), None)['ip_address']
@@ -298,7 +298,7 @@
         ):
             kwargs = {'ipv6_ra_mode': ra_mode,
                       'ipv6_address_mode': add_mode}
-            kwargs = {k: v for k, v in six.iteritems(kwargs) if v}
+            kwargs = dict((k, v) for k, v in six.iteritems(kwargs) if v)
             subnet = self.create_subnet(self.network, **kwargs)
             ip_range = netaddr.IPRange(subnet["allocation_pools"][0]["start"],
                                        subnet["allocation_pools"][0]["end"])
@@ -376,7 +376,7 @@
         ):
             kwargs = {'ipv6_ra_mode': ra_mode,
                       'ipv6_address_mode': add_mode}
-            kwargs = {k: v for k, v in six.iteritems(kwargs) if v}
+            kwargs = dict((k, v) for k, v in six.iteritems(kwargs) if v)
             subnet, port = self._create_subnet_router(kwargs)
             port_ip = next(iter(port['fixed_ips']), None)['ip_address']
             self._clean_network()
diff --git a/tempest/thirdparty/boto/test_ec2_instance_run.py b/tempest/thirdparty/boto/test_ec2_instance_run.py
index 49a1854..6c1b362 100644
--- a/tempest/thirdparty/boto/test_ec2_instance_run.py
+++ b/tempest/thirdparty/boto/test_ec2_instance_run.py
@@ -175,23 +175,23 @@
             instance.add_tag('key1', value='value1')
 
         tags = self.ec2_client.get_all_tags()
-        td = {item.name: item.value for item in tags}
+        td = dict((item.name, item.value) for item in tags)
 
         self.assertIn('key1', td)
         self.assertEqual('value1', td['key1'])
 
         tags = self.ec2_client.get_all_tags(filters={'key': 'key1'})
-        td = {item.name: item.value for item in tags}
+        td = dict((item.name, item.value) for item in tags)
         self.assertIn('key1', td)
         self.assertEqual('value1', td['key1'])
 
         tags = self.ec2_client.get_all_tags(filters={'value': 'value1'})
-        td = {item.name: item.value for item in tags}
+        td = dict((item.name, item.value) for item in tags)
         self.assertIn('key1', td)
         self.assertEqual('value1', td['key1'])
 
         tags = self.ec2_client.get_all_tags(filters={'key': 'value2'})
-        td = {item.name: item.value for item in tags}
+        td = dict((item.name, item.value) for item in tags)
         self.assertNotIn('key1', td)
 
         for instance in reservation.instances: