Object-ify APIv3 availability_zone extension

This makes the availablility_zone extension use the Service object
for looking up service details instead of a direct-to-database
call.

Related to blueprint compute-manager-objects-juno

Change-Id: I3091bc06a74e32871a743a831ab3db23220ae8f8
Fix log debug statement in compute manager

The patch does the following:
1. Ensures that there are no translations with log debug messages
2. Uses ',' instead of '%' with the parameters passed to the debug
   message
3. Aligns the debug messages

TrivialFix

Change-Id: Id35a969b92fb92487c8b169ff0729ab1851d30f1
Standardize logging for nova.virt.libvirt

 - add log translation hints for warning, error and info levels
 - remove use of % as a string formatter, use the log functionality
   instead
 - move from LOG.warning to LOG.warn

Log translation is motivated by oslo's move to prioritized
translation of strings, as documented at
https://wiki.openstack.org/wiki/LoggingStandards#Log_Translation

Change-Id: I61ab8dbcdb73795538ea9d60c0c9d00c425ee1a5
Merge "Fix log debug statement in compute manager"
Merge "Standardize logging for nova.virt.libvirt"
Merge "Object-ify APIv3 availability_zone extension"