api: remove unused function

Change-Id: I2ef2711d2ceffd3a3c375a137ff07f9ad0e18aeb
Use mtu setting from table instead of flag

Adds mtu to argument lists of key methods and configuration of vlan
interface. Also adds deprecation notice to the "help" info for the file
based network_device_mtu configuration property.

Partially-implements blueprint better-support-for-multiple-networks

Change-Id: Ia401eb95ce8c81d104e59b0348e3474655b9a992
libvirt: more efficient method to list domains on host

The current libvirt driver code uses the legacy APIs for
enumerating domains on a host. These have a number of
problems

 - O(N) APIs calls are required to list N domains which
   is slow as number of domains increases
 - Race wrt start/stop of guests gives many problems
     - Domains guest lost between listDomainsIDs() and
       listDefinedDomains()
     - Domains disappear before lookupById/Name is
       called
     - Disagreement between numOfDomains and listDomainsIDs
       and numOfDefinedDomains and listDefinedDomains

Blueprint: libvirt-domain-listing-speedup
Change-Id: Id31f3071dfb10e33c51501b860a03f8975bbe812
Fix more re-definitions and enable F811/F813 in gate

Additional issues found by flake8 by enabling F811 and
F813. There was only one F813 list comprehension redefinition.
The rest of the changes were F811 redefinition of unused name
violations.

Change-Id: Iad5406c149ab21d360b7e98899a92082197c8c17
Merge "libvirt: more efficient method to list domains on host"
Merge "Fix more re-definitions and enable F811/F813 in gate"
Merge "api: remove unused function"
Merge "Use mtu setting from table instead of flag"