tests: fix timer scaling in wait-on-file When using the default test timeouts, wait-on-file would not wait for $n seconds, but $n/100 seconds. This resulted in easy timeouts on even moderately busy fast machines. Fix the scaling to apply in all cases. Adjust the stepping slightly to be nicer to systems with the historic 100Hz time base to ensure that the scheduler actually switches to a different process and gives them time to work. Differential Revision: https://phab.mercurial-scm.org/D8505