tests: Allow resetting the value of a counter
tests: Allow resetting the value of a counter

This is useful when you want to check the event count delta after doing
some operations.

qida/fsnotify,masahide/fsnotify,justintung/fsnotify,fsnotify/fsnotify,fsnotify/fsnotify,scalingdata/fsnotify-v1,opsmatic/fsnotify,wheelcomplex/fsnotify,fsnotify/fsnotify,jsix/fsnotify,streamrail/fsnotify,springning/fsnotify,treejames/fsnotify,beni55/fsnotify,omeid/fsnotify,beni55/fsnotify-1,FactomProject/fsnotify,mingshun/fsnotify,howeyc/fsnotify