object-ify API v2 availability_zone extension

This change converts the availability_zone extension to use the
Service object instead of direct database access.

Related to blueprint compute-manager-objects-juno

Change-Id: If5baafd8ec85be1ea1cd6580ae10ef3d51366c9c
Update dev env docs on libvirt-dev(el) requirement

Commit 8f505b85268adc226ec0a83826c2d13edcbe3d7c added
a test requirement on libvirt-python which requires
libvirt-dev(el) being installed, so update the docs
to add that package for the distro.

Change-Id: I7169d3c78a6babe6e20c0dc35874167d0bfee922
libvirt re-define guest with wrong XML document

In the nova/virt/libvirt/driver.py file, the '_live_snapshot' and
'_swap_volume' methods have the following code flow
  xml = dom.XMLDesc(0)
  dom.undefine()
  dom.blockRebase()
  dom.defineXML(xml)
The reason for this is that 'blockRebase' requires the guest to be
transient, so we must temporarily delete the persistent config and
then re-create it later.
Unfortunately this code is using the wrong XML document when
re-creating the persistent config. 'dom.XMLDesc(0)' will return the
guest XML document based on the current guest state. Since the guest
is running in both these cases, it will get getting the *live* XML
instead of the persistent XML.So these methods are deleting the
persistent XML and replacing it with the live XML. These two
different XML documents are not guaranteed to contain the same
information.
As a second problem, it is not requesting inclusion of security
information, so any SPICE/VNC password set in the persistent XML
is getting lost.

Change-Id: I4b4e0990ca6c07a9215766f994884a1fb18f3a41
Closes-Bug: #1346191
Add trace logging to allocate_fixed_ip

The address is being logged as None in some cases
that are failing in grenade jobs so this adds more
trace logging to the base network manager's
allocate_fixed_ip method so we can see which paths
are being taken in the code and what the outputs
are.

Change-Id: I37de4b3bbb9e51b57eb4d048e05fc00382eed23d
Related-Bug: #1349617
Merge "object-ify API v2 availability_zone extension"
Merge "Update dev env docs on libvirt-dev(el) requirement"
Merge "Add trace logging to allocate_fixed_ip"
Merge "libvirt re-define guest with wrong XML document"