timers: setInterval interval includes cb duration

setInterval callback should be scheduled on the interval

Fixes: https://github.com/nodejs/node/issues/7346

PR-URL: https://github.com/nodejs/node/pull/14815
Fixes: https://github.com/nodejs/node/issues/7346


Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: Jeremiah Senkpiel <fishrock123@rocketmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Michael Dawson <michael_dawson@ca.ibm.com>