Move rebuild to conductor and add find host logic

[*] Move rebuild instance to conductor task api will help
    in consolidating the logic for both evacuate instance and
    rebuild instance. Rebuild instance and evacuate instance
    uses the conductor task api for rebuild instance workflow.
[*] Add logic required to support rebuild without host.
    (used by evacuate)
[*] Refactor rebuild action to pass the instance host as argument,
    instead of None.

Evacuate and Rebuild will behave the same way as today.
Modifications for the new feature in API will be implemented in
new patches.

Partial Implements: blueprint find-host-and-evacuate-instance

Change-Id: I4b1a9c2227574db7179441d531a49145f213ea87
Co-Authored-By: Juan M. Olle <juan.m.olle@intel.com>
Co-Authored-By: Anuj Mathur <anujm@thoughtworks.com>
Co-Authored-By: Navneet Kumar <navneetk@thoughtworks.com>
Co-Authored-By: Claxton Correya <claxton@gmail.com>
libvirt: Save device_path in connection_info when booting from volume

If you boot an instance from a volume and later terminate it, the
libvirt volume driver disconnect_volume method does not have the
'device_path' key in connection_info['data'].  However, if you
attach a volume to an existing instance and then detach it,
the disconnect_volume method would have the 'device_path' key in
connection_info['data'].  Having the 'device_path' key would be
useful for some volume drivers to determine the device path of the
volume.  This patch saves the 'device_path' in connection_info['data']
when _create_domain_and_network is called, so it could be later used.

Change-Id: I8ebb5f3c2e7a81b11d776f8c0a15f3491ed273be
Closes-Bug: #1291007
VMware: consolidate datastore code

This is largely a straight-forward code movement.
Given that we have utility classes/code in ds_util.py, it makes sense
to move the remaining datastore-related code in vm_util.py to ds_util.py
as well.

partial blueprint vmware-spawn-refactor
Change-Id: I2ede44306acf91a13f2ff6f0d8f210642a1c1e69
update ignore list for pep8

Remove H803 as Nova does not run into that issue. Sort
the rest of the items (E129 was out of place).

Change-Id: I6c2537dd27c947e36ebf37eb3b5c8a1ab8b026a1
Merge "VMware: consolidate datastore code"
Merge "libvirt: Save device_path in connection_info when booting from volume"
Merge "Move rebuild to conductor and add find host logic"
Merge "update ignore list for pep8"