"when" directive should not allow staging of input files for a process, if the criteria are not met

[fstrozzi]

Hello,
the "when" directive seems to be allowing staging input files even for processes that are not fulfilling the criteria specified. I think a better behaviour could be to entirely skip the process if the conditions under "when" are not met, given that for certain processes the inputs staging can take up quite some time and resources, especially if the files need to be copied or collected over the network.

Thanks!

[pditommaso]

related to #265