Removed the node attribute "developer_mode"

This should only be set as an environment variable,
set within Chef.
forced evaluation of the Node Attribute.

"developer_mode" should only be used if it is true.
Merge pull request #301 from cloudnull/DE199-grizzly

Merged automatically by jenkins after successful build test
Add fixed_ip_disassociate_timeout attributes

Depends on rcbops-cookbooks/nova-network#42
Merge pull request #302 from DavidWittman/fixed-ip-disassociate

Merged automatically by jenkins after successful build test
Merge branch 'grizzly' of https://github.com/rcbops-cookbooks/nova into grizzly
minor doc update