Remove LOG outputs from v2.1 API layer

There are some debug/audit log messages about normal API operations
in each API method, but Nova WSGI framework has already output the
similar messages. So these messages are meaningless, and this patch
removes them.
This patch removes LOG outputs of InterfaceAttachFailed cases also,
because they are already output on driver layer(vmwareapi, libvirt)
and duplicated now.

Partially implements blueprint v2-on-v3-api

Change-Id: Ib645d1c320e6104bad34c2d7238db399e8d1ea42
Network: manage neutron client better in allocate_for_instance

A neutron client only needs to be created twice in the aforementioned
method. The first time is for the tenant and the second, if necessary,
is for the admin. This is in the event that a port binding extension
is supported (only an admin user can read this).

In addition to this is a client exists then the method will make use
of it passing it to all internal methods called. This will enable them
to reuse that client instead of creating a new one.

Change-Id: Ia826199ea600ab55447ca4e8a78738c21b473efa
Closes-bug: #1377647
Compute: maint: adjust code to use instance object format

Update the code to use instance object format instead of dict format.

TrivialFix

Change-Id: I98814c5960f6fa83e3ace36039783ea36e39b3f9
Add API validation schema for disk_config

This patch adds API validation schema for disk_config.

This patch also modify TestServersExtensionSchema to load
disk_config extension so that update, rebuild & resize
extension schema loading can be verified.

Partially implements blueprint v2-on-v3-api

Change-Id: Ib687a8e4e8b173c32bcd19e396b23fbf2f3319c6
Merge "Add API validation schema for disk_config"
Merge "Remove LOG outputs from v2.1 API layer"
Merge "Compute: maint: adjust code to use instance object format"
Merge "Network: manage neutron client better in allocate_for_instance"