Ubuntu does not support anymore package chkconfig

From release 12.10, Ubuntu removed the support of chkconfig package.
I set a specific install chkconfig command in case it fails, it fails
alone.
Merge pull request #28 from Doude/chkconfig_and_Ubuntu

Ubuntu does not support anymore package chkconfig
devstack changes to have it work with github changes
Add --rabbit_password argument to api-server