mr.awsome should do some sanity check before starting an instance

[kiddouk]

When starting an instance,

mr.awsome should first check if it will match the requirements like volume availability / ip prewsent in the pool (and by extension to my previous pull requests) if the load balancer exists in the same zone.

If not, then mr.awsome should prevent the instance to start unless a config option "force_start" (or something like that) is specified in the conf.