Fix openCL device check on tests

the line
```python
openCLDevices = [device for device in clsim.I3CLSimOpenCLDevice.GetAllDevices() if device.cpu]
```
return an empty array even if openCL device available

if device.cpu check fail, just removing it allow to run tests successfully 
```python
openCLDevices = [device for device in clsim.I3CLSimOpenCLDevice.GetAllDevices()]
```
My installation : Tesla M2075