waitForJobs in src/Ganeti/Jobs.hs has an integer overflow that (at least on
amd64) causes it to break after waiting for ~10 minutes. This results in hbal
sleeping forever (when compiled with squeeze's ghc 6.12.1) or crashing (when
compiled with precise's ghc 7.4.1) whenever it has to wait ~10 minutes for a
jobset to complete.

Thanks to gjo@google.com for finding the bug and suggesting the fix.

Fixes Issue 717.

Signed-off-by: Michele Tartara <mtartara@google.com>
Reviewed-by: Klaus Aehlig <aehlig@google.com>