Fix FloatingIP.save() passing FixedIP object to sqlalchemy

This prevents the FloatingIP.save() method from passing the
calculated FixedIP object to the sqlalchemy floating_ip_update()
function, which would expect it to be an SA object. It also
aborts any attempt to save the object with a modified fixed_ip_id
linkage, as associate/disassociate should be used for that.

This also fixes a bug where FloatingIP expects the result of
floating_ip_update() to be a FloatingIp SA object.

Added missing import to allow tests to work in stable/icehouse.

Change-Id: I065caedf4d81c8583a3b390934a1d403cf2e87bd
Closes-bug: #1334164
(cherry picked from commit 48de2895b9a550a0944b31212349275605a4061d)
Merge "Fix FloatingIP.save() passing FixedIP object to sqlalchemy" into stable/icehouse
libvirt: add support for memory backing parameters

Add a libvirt config class for dealing with the XML elements
under the <memoryBacking> section of the guest schema.

Blueprint: virt-driver-large-pages
Change-Id: Icd89508671a8951bed480b901b2d12d44ebb7cab
Define constants for the VIF model types

Define constants for the common VIF model types. This will
ensure that all of the drivers will make use of the same values.

Change-Id: I2099bbe92906ac0b1b54f1819113b33565e78980
Add VIF_VHOSTUSER

This is based on a new QEMU feature called vhost-user for connecting
to a user-space vswitch via a unix socket.

Change-Id: I0a11e89d3a0bbdfccac569c09009e576ea2e1173
Signed-off-by: Michele Paolino <m.paolino@virtualopensystems.com>
libvirt: enable hugepages config from flavor mem_hugepages

Signed-off-by: Nikolay Nikolaev <n.nikolaev@virtualopensystems.com>