[Piglit] [PATCH 1/2] framework: When a test fails, try it again to see if it's consistent.

[Chad Versace]

Series is
Reviewed-by: Chad Versace <chad.versace at linux.intel.com>

I tested the "unstable" patch with `./piglit-run.py -t fbo-sys -t front -t timer`,
and the html summary looks good to me.