Testings do not report failed task submissions

With StarPU, execute the following:

chameleon_stesting -o potrf -b 320 -n 3200 -H --niter 1 -g 2 -t 0

so no CPUs to execute tasks, just two GPUs.

It floods the output with StarPU messages:

[starpu][_starpu_task_insert_v] submission of task 0x5573f91cb690 with codelet 0x5573f8d97340 failed (symbol `splgsy') (err: ENODEV)

Which is normal, since zplglsy has only a CPU codelet.

However, it does not affect the results:

 Id Function     threads gpus  P  Q mtxfmt  nb uplo        n   lda       seedA          tsub          time        gflops
  0 spotrf             0    2  1  1      0 320 Upper    3200  3200   846930886  0.000000e+00  1.062311e-02  1.028680e+03

while the gflops should be -1 since there was a failure.

The problem is we don't check the return value of insert_task calls (for instance here) and we always return CHAMELEON_SUCCESS in the calling function (for instance here).