wait_on jiffy only works for single files.

[cerebis]

This little jiffy waits for file output and only accepts a single file as an argument. For the current time series workflow, this would need to be extended to deal with multiple read-pairs.

It was only added to deal quickly with the unresolved issue of incomplete file generation in metaART when a running process is interrupted, going unnoticed, but workflows continuing on. In reality, it was added while using the Scons/nestly approach and was possibly only an issue with that system on a distributed execution environment.

We should investigate whether killing running metaARTs with meta-sweeper can still produce incomplete read-sets.

This jiffy has been removed from deconvolute-timeseries.nf