test_session: Simplify AlreadyRegistered using a TestSessionPair.
test_session: Simplify AlreadyRegistered using a TestSessionPair.

Change-Id: I5caba1f453f4508f9b84d3e4bc8b6283d5a6f221
Reviewed-on: http://gerrit.aldebaran.lan:8080/15275
Reviewed-by: cgestes <ddb78fe00abb42f91254c16a0860e38eb0781789@aldebaran-robotics.com>
Reviewed-by: mnottale <e3ccf1b6558404e921a21fa09cebb1153b50ec36@aldebaran-robotics.com>
Tested-by: mnottale <e3ccf1b6558404e921a21fa09cebb1153b50ec36@aldebaran-robotics.com>

aldebaran/libqi,vbarbaresi/libqi,aldebaran/libqi,aldebaran/libqi-java,aldebaran/libqi,aldebaran/libqi-java,bsautron/libqi,aldebaran/libqi-java