Two fixes reported by clang

Hi Jens,

I've been running Clang 3.3 on fio and after reading many false positive errors, I found 1 real mistake and an improvement to make on the code.

Please find my branch here :
https://github.com/enovance/fio/tree/erwan/clang

Note that my previous emails about init & options.c were coming also from this clang pass.

Erwan,

Both of these look good, applied! Thanks.

Jens Axboe