destroying a primary service does not cause subordinate to depart

[Clint Byrum]

I am working on some enhancements to nagios and this scenario came up.

nagios == lp:~clint-fewbar/charms/precise/nagios/add-monitors-2
mysql == lp:~clint-fewbar/charms/precise/mysql/add-monitors
nrpe == lp:~clint-fewbar/charms/precise/nrpe/trunk

juju deploy nagios
juju deploy mysql
juju deploy nrpe
juju add-relation nrpe mysql
juju add-relation nrpe:monitors nagios:monitors
juju add-relation mysql:monitors nagios:monitors

This configures nagios to monitors mysql-0 using both nrpe and straight remote mysql pings.

Then I want to clean this up:

juju destroy-service mysql

This properly fires the monitors-relation-broken on nagios for the mysql<->nagios connection, but I never get a departed event for the nrpe unit that was just removed.