Fix a corner case where no tests failed but status still > 0
Fix a corner case where no tests failed but status still > 0

For example, when disk is full.

See fate.ffmpeg.org/report.cgi?time=20150405122744&slot=aarch64-linux-qemu-ubuntu-gcc-4.8a-n2.5

TimothyGu/fateserver-node,TimothyGu/fateserver-node