heat.engine.os clients duplicate client args logic

[Kanagaraj Manickam]

Heat has client plugins for those supported OpenStack resources under heat.engine.clients.os and many of these plugins duplicate the logic of forming the arguments required to create the given client.

Following is the args logic being used across these client plugins: (these args are used by the keystone client, from which all other OpenStack clients are derived)

        args = {
            'auth_url': con.auth_url,
            'service_type': 'metering',
            'project_id': con.tenant,
            'token': lambda: self.auth_token,
            'endpoint_type': endpoint_type,
            'os_endpoint': endpoint,
            'cacert': self._get_client_option('ceilometer', 'ca_file'),
            'cert_file': self._get_client_option('ceilometer', 'cert_file'),
            'key_file': self._get_client_option('ceilometer', 'key_file'),
            'insecure': self._get_client_option('ceilometer', 'insecure')
        }

Here only the service name, type are varying for the given OpenStack service where as other parameters are same across. endpoint type and endpoint could be retrieved based on these service name and type.

So this bug is filed to remove the duplication of this logic. and there by reduce the maintenance effort in future.