Description of problem:

If beakerd is unable to schedule a machine (for example power control fails), and the machine does not have an owner the following traceback will be thrown:

2011-03-29 09:47:46,304 beakerd DEBUG Entering scheduled_recipes routine
2011-03-29 09:47:46,304 beakerd INFO scheduled_recipes: RS:3247
2011-03-29 09:49:36,702 beakerd ERROR Cobbler task failed for recipe 4624: 'Cobbler Task:2011-03-29_094746_power Failed'
2011-03-29 09:49:36,708 beakerd ERROR Failed to commit in scheduled_recipes
Traceback (most recent call last):
  File "/usr/lib/python2.4/site-packages/bkr/server/tools/beakerd.py", line 486, in scheduled_recipes
    recipe.system.mark_broken(reason=str(e), recipe=recipe)
  File "/usr/lib/python2.4/site-packages/bkr/server/model.py", line 2377, in mark_broken
    mail.broken_system_notify(self, reason, recipe)
  File "/usr/lib/python2.4/site-packages/bkr/server/mail.py", line 112, in broken_system_notify
    send_mail(sender, system.owner.email_address,
AttributeError: 'NoneType' object has no attribute 'email_address'
2011-03-29 09:49:36,709 beakerd DEBUG Exiting scheduled_recipes routine


Version-Release number of selected component (if applicable):
0.6.7


Steps to Reproduce:
1. set the owner to None and misconfigure power settings for a system
2. schedule against that machine

Actual results:
Job stays in scheduled state and keeps trying to schedule it.

Expected results:
Scheduler should abort job