Fix libvirt watchdog support

[OpenStack Infra]

https://review.openstack.org/134217
commit dbc348d296cbbb03650f77f6ef29b55635162c15
Author: pkholkin <email address hidden>
Date: Fri Sep 12 19:31:54 2014 +0400

    Fix libvirt watchdog support

    Using the flavor extra_specs property "hw_watchdog_action" was broken.
    Scheduling of a new instance always failed with NoValidHostFound error
    because of ComputeCapabilitiesFilter, which treated this property as a
    host capability to be checked.

    Commit f0ff4d51057080e769407e873e5ed212f15b773d caused the problem.

    To fix this watchdog_action property is put into 'hw:' scope, so
    that it will be ignored by ComputeCapabilitiesFilter in scheduler and
    handled in libvirt driver. The doc must be fixed accordingly.

    Now driver accepts both 'hw_watchdog_action' and
    'hw:watchdog_action', tests were edited for these cases.
    Were added TODO items to delete the compat code in L release.

    DocImpact
    Closes-Bug: #1367344

    Conflicts:
     nova/tests/virt/libvirt/test_libvirt.py

    Change-Id: Ic5344ec34a130ee5a0ed2c7348af0b9d79e3508e
    (cherry picked from commit 79bfb1bf343484e98aa36dcc663a5370baf4cab7)

[Gauvain Pocentek (gpocentek)]

admin-guide-cloud documents this extra spec.

[venkatamahesh (venkatamaheshkotha)]

These changes are updated at :
https://github.com/openstack/openstack-manuals/blob/master/doc/admin-guide-cloud/source/compute-flavors.rst

[Alexandra Settle (alexandra-settle)]

This has been updated: http://docs.openstack.org/admin-guide/compute-flavors.html

Thank you :)