Fix race in MessageDispatcher::messagePendingDisconnect.
Fix race in MessageDispatcher::messagePendingDisconnect.

Change-Id: If173fcf1185e9c162992b0a47765ee8c31bd65ad
Reviewed-on: http://gerrit.aldebaran.lan/20267
Reviewed-by: mnottale <e3ccf1b6558404e921a21fa09cebb1153b50ec36@aldebaran-robotics.com>
Tested-by: mnottale <e3ccf1b6558404e921a21fa09cebb1153b50ec36@aldebaran-robotics.com>

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