Utilize neutron sanity_check tool after deployment

Neutron has a sanity_check tool that can be used to verify deployment and whether it fits upstream expectations, based on current configuration: http://otherwiseguy.tumblr.com/post/89880974499/neutron-external-sanity-checks

If you pass it configuration files that are used in neutron deployment, then it will execute all the checks it knows about and that are relevant to current setup (f.e. it won't execute ovs checks for non-ovs deployments) and report any issues that it found, on stderr, and thru return code.

It would be useful to have packstack execute the tool after deployment to check that upstream expectations against underlying operating system and configuration values used are fulfilled. Packstack would then fail or report an error in any other way suitable to installer.

Users may want to disable the sanity checks in case they know their environment is fine, or they expect it to fail due to some known bugs, so the check would be optional or even disabled by default.