ENYO-2935, ENYO-2044: fix _too many open files_ using `graceful-fs`

Also see:

* https://enyojs.atlassian.net/browse/ENYO-3061
* https://npmjs.org/package/graceful-fs

Enyo-DCO-1.1-Signed-off-by: Francois-Xavier KOWALSKI <francois-xavier.kowalski@hp.com>