two chroot related fixes

- Pass SCR root path to stdio agents [bnc#879365](https://bugzilla.novell.com/show_bug.cgi?id=879365).
- If aborting on a SCRAgent::targetPath assertion, log it [bnc#891053](https://bugzilla.novell.com/show_bug.cgi?id=891053)

Good point. I considered rewriting that line, but I did not want to touch that code much: simply verified that it indeed is an assignment and not a comparison and silenced the warning.