watch: add --no-clean to nyc args on change tests
watch: add --no-clean to nyc args on change tests

Not sure how this went so long without me noticing.  Probably because I
usually use a coverage-map, so one test = 100% of one file.

isaacs/node-tap,evanlucas/node-tap,isaacs/node-tap,tapjs/node-tap,evanlucas/node-tap,tapjs/node-tap