Do not limit retries for re-sumbissions with maxErrors

[manuelesimi]

Currently, if maxErrors is set to a value lesser than maxRetries, only up to maxErrrors re-submissions are attempted for a process. From a user's perspective, this is a bit confusing, especially if only maxRetries is set and maxErrors is left to its default value (1). maxErrors should not limit the number of possible resubmissions.

From outside the box, I see to alternative ways to go:

1. a conventional value (e.g. -1) for maxErrors that tells nextflow to ignore the errors limit. The risk with this option is that a process execution could go on forever with re-submissions. To avoid that, it should be allowed only when maxRetries is also set.
2. when maxRetries is set, maxErrors is ignored, regardless its value. This could be seen as a sort of priority between them. The drawback is that the maximum number of re-submission is determined by maxRetries * number of execution instances.

[pditommaso]

I think the first alternative is the best one. Indeed, maxErrors should be by default -1 so it does not check the errors upper limit.

Also maxRetries should by default 1, in this way the same task can be re-execute only one time, and it's coherent with the re-try semantic.

Then a user can set both maxErrors and maxRetries to higher values to tune the error strategy depending its requirements.

[pditommaso]

Now it is possible to set maxErrors to -1 to ignore it. However the default has not changed.