DE170: fix notifications for nova_conf

nova_conf lwrp currently encapsulates two templates; services should
therefore subscribe the lwrp and not one of its embedded resources.
for chef 11, `use_inline_resources' is required for this to work (to
notify top-level resources). also removed embedded `log' resource as it
unconditionally marks the lwr as changed every time.
Add disk_allocation_ratio attribute

This commit adds the disk_allocation_ratio attribute to the Nova
config. This allows Nova to schedule instances on hosts only if
there is sufficient disk space available for root and ephemeral
storage.

Note that this attribute is only enabled when DiskFilter is added
to node["nova"]["platform"]["nova_scheduler_default_filters"].
Merge pull request #279 from invsblduck/DE170_fix_nova_conf_notifies

DE170: fix notifications for nova_conf
Merge pull request #295 from DavidWittman/disk-allocation-ratio

Add disk_allocation_ratio attribute