test_signal: Be more deterministic
test_signal: Be more deterministic

Change-Id: Ife92854ca431cc5951e96db2c2804979512897ce
Reviewed-on: http://gerrit.aldebaran.lan:8080/9597
Reviewed-by: cgestes <ddb78fe00abb42f91254c16a0860e38eb0781789@aldebaran-robotics.com>
Tested-by: mnottale <e3ccf1b6558404e921a21fa09cebb1153b50ec36@aldebaran-robotics.com>

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