Prevent Remote Command run on non-prepared systems. Better error handling..

Systems/Details/Remote Command will fail in a not nice way, when target system did not activated provisioning or remote script availability. This patch fixes it.

Example:
![screen shot 2014-03-13 at 10 24 24 pm](https://f.cloud.github.com/assets/1073714/2415479/1acb203c-aaf6-11e3-90e8-5c411ba5e636.png)