python-neutronclient 6.1.0 has changed the output format for some
fields [1], breaking the neutron_subnet provider. This patch adds support
for the new output, while keeping backwards compatibility.
[1]
Old output:
allocation_pools="{\"start\": \"172.24.4.2\", \"end\": \"172.24.4.254\"}"
New output:
allocation_pools="[{u'start': u'172.24.4.2', u'end': u'172.24.4.254'}]"
Change-Id: Iad1bd41541a46b306d01f3343710080e3e93d8df
deaaa35b63