Reset errno before calling posix_spawn - Test did't pass on mac, that's aukward.
Reset errno before calling posix_spawn
- Test did't pass on mac, that's aukward.

Change-Id: I5d579a725f6288671f16924fd62c94897f1b5561
Reviewed-on: http://gerrit.aldebaran.lan:8080/3128
Reviewed-by: proullon <ffff9135679d397f48dd743107119b1f6fc32d3d@aldebaran-robotics.com>
Tested-by: proullon <ffff9135679d397f48dd743107119b1f6fc32d3d@aldebaran-robotics.com>

aldebaran/libqi,vbarbaresi/libqi,bsautron/libqi,aldebaran/libqi,aldebaran/libqi