Temporary fix to setting public_ips

A few different problems were encountered in the last few hours, most of them
have been fixed:
 * Quantum properly associated floating IPs, but nova does not list them under
 extra['addresses'], as a result no public IP is assigned. It takes more than
 10-15 minutes before quantum/nova starts listing the floating IP in the
 'addresses' space on nova. To combat this we use the metadata 'public_ip'
 that we set after assigning a floating IP.

 * Deployment tasks that failed would call retry twice, so 2 tasks would start
   on retry 1 and 3 tasks would start on retry 2. This has been fixed.

 * _connect_to_nova had a trailing comma that changed a string to a tuple. this
   has been corrected
	modified:   service/drivers/common.py
	modified:   service/drivers/openstack_driver.py
	modified:   service/tasks/driver.py