At the moment, we can only use crank if the pending entry is in the
future. This patch leaves the clock time to the same point if the
pending entry was in the past. This still execute a single entry. This
will be needed for the jitterbuffer, since as soon as we stop waking up
the jitterbuffer when the timer is reschedule later, we may endup with
such case in the unit tests.

Related to #608