Add a module_utils OpenStack Cloud constructor (#20974)

Start using this to construct shade OpenStack Cloud objects in a
consistent manner. This will let us centralize things like dealing with
password arguments and whatnot. It also allows us to introduce the
ability to pass a fully formed config dict directly to the module.

Migrate all OpenStack modules to use openstack_cloud_from_module.

Have it return the shade library since it's responsible for
importing shade and shade is needed for the exceptions.

Only pull specific OpenStack arguments for the constructor

Rather than passing **module.params to the shade constructor, pull out
only the values that make sense. This should prevent the issues with
module parameters stepping on shade parameters.

Replace module.params.pop with module.params.get

We don't need to pop these anymore since the shade constructor is now
using opt-in values.

Using real urls is ungood. Use example.com domains. Also, get rid of the
antiquated port numbers.

test/units/modules/cloud/openstack/test_os_server.py

@@ -81,6 +81,9 @@ class FakeCloud (object):
     def get_network(self, name):
         return self._find(self.networks, name)
 
+    def get_openstack_vars(self, server):
+        return server
+
     create_server = mock.MagicMock()