Catch SystemCallError during blimpy provision for retry

Previously we were only catching Fog::Errors::Error exceptions, this patch
makes sure that system call failures are also caught, so things like connection
refused and no route to host which are generally transient, are caught and
retried properly.

Signed-off-by: Ken Barber <ken@bob.sh>
Merge pull request #84 from kbarber/maint/master/retry-blimpy-on-systemcall-errors

Catch SystemCallError during blimpy provision for retry