Re-enable the roundtrip test in the buildbots.

.jenkins/jenkins_buildbot_python2.sh

@@ -2,8 +2,6 @@
 
 BUILDBOT_DIR=$WORKSPACE/nightly_build
 THEANO_PARAM="theano --with-timer --timer-top-n 10"
-# Exclude MPI tests that cannot complete properly
-THEANO_PARAM="${THEANO_PARAM} -e test_mpi_roundtrip"
 export THEANO_FLAGS=init_gpu_device=cuda
 
 # CUDA

.jenkins/jenkins_buildbot_python2_debug.sh

@@ -2,8 +2,6 @@
 
 BUILDBOT_DIR=$WORKSPACE/nightly_build
 THEANO_PARAM="theano --with-timer --timer-top-n 10 -v"
-# Exclude MPI tests that cannot complete properly
-THEANO_PARAM="${THEANO_PARAM} -e test_mpi_roundtrip"
 export THEANO_FLAGS=init_gpu_device=cuda
 
 # CUDA

.jenkins/jenkins_buildbot_python3.sh

@@ -2,8 +2,6 @@
 
 BUILDBOT_DIR=$WORKSPACE/nightly_build
 THEANO_PARAM="theano --with-timer --timer-top-n 10"
-# Exclude MPI tests that cannot complete properly
-THEANO_PARAM="${THEANO_PARAM} -e test_mpi_roundtrip"
 COMPILEDIR=$HOME/.theano/buildbot_theano_python3
 # Set test reports using nosetests xunit
 XUNIT="--with-xunit --xunit-file="