Tests using gtest only work with some lattice sizes

[martin-ueding]

For some unknown reason, the tests work fine with

mpirun -n 1 tests-gtest/tests_g -by 4 -bz 4 -pxy 1 -pxyz 0 -minct 1 -c 2 -sy 1 -sz 2 -x 8 -y 4 -z 4 -t 4

but fail with other lattice configurations.