This reverts commit f939d92e.

this is to reduce load when heavy backup or migrate tasks are run by
the queue daemon. the NICE value is customizable in /etc/default/hosting-queued

Conflicts:
	hosting_queue_runner.drush.inc

Conflicts:
	hosting_queue_runner.drush.inc

This reverts commit 5d131475.

this reduces latency (one less sleep(1) call), the number of SQL
requests (one request per N tasks, where N is the default argument of
hosting_get_new_tasks()) and probably use less memory because we don't
do the wider loop all the time

this means, however, we need to check the time in the inner loop too

we do not need to fork, as we do not need the PID to wait for it,
thanks to pcntl_wait().

now it interrupts child tasks, which isn't good, but can be improved