EcalRawToDigiGPU should fail gracefully if CUDA is not available

[fwyzard]

EcalRawToDigiGPU should fail gracefully if CUDA is not available, or if the driver is not recent enough.

Trying to run on a machine without GPUs or with an older version of CUDA 10.1 results in

%MSG-w CUDAService:  (NoModuleName) 11-May-2020 21:52:33 CEST pre-events
Failed to initialize the CUDA runtime.
Disabling the CUDAService.
%MSG
11-May-2020 21:52:37 CEST  Initiating request to open file file:step2.root
11-May-2020 21:52:38 CEST  Successfully opened file file:step2.root

std::bad_alloc exception
11-May-2020 21:52:38 CEST  Closed file file:step2.root
----- Begin Fatal Exception 11-May-2020 21:52:38 CEST-----------------------
An exception of category 'BadAlloc' occurred while
   [0] Constructing the EventProcessor
   [1] Constructing module: class=EcalRawToDigiGPU label='ecalDigisGPU'
Exception Message:
A std::bad_alloc exception was thrown.
The job has probably exhausted the virtual memory available to the process.
----- End Fatal Exception -------------------------------------------------

[vkhristenko]

not needed after #502

[fwyzard]

Thanks