Follow hacking about import

This patch follows the rules about import in HACING.rst
https://github.com/openstack/savanna/blob/master/HACKING.rst#imports

 * reorder imports
 * Add missing blank lines before code

Change-Id: I9cd14fb3c3bf9567c6fee772a1b3188baf1bcbd9

savanna/config.py

@@ -18,6 +18,7 @@ from oslo.config import cfg
 from savanna.openstack.common import log
 from savanna import version
 
+
 cli_opts = [
     cfg.StrOpt('host', default='',
                help='Hostname of IP address that will be used to listen on'),