[ktl/workflow.py] add default assignee for 'upload-to-ppa'
This should fix a long standing bug that occurs while creating the raspi2
derivative tracking bug:
Traceback (most recent call last):
File "/home/miguel/kernel/kteam-tools/stable/sb/workflow_engine.py", line 855, in handle_derivatives
bug = tb.open(der_pkg, '<version to be filled>', True, taskobj.bug.id, series)
File "/home/miguel/kernel/kteam-tools/stable/ktl/tracking_bug.py", line 266, in open
assignee = self.wf.assignee(package, task_name, devel_series)
File "/home/miguel/kernel/kteam-tools/stable/ktl/workflow.py", line 358, in assignee
return db['default']['task_assignment'][taskname]
KeyError: u'upload-to-ppa'
Signed-off-by: Luis Henriques <email address hidden>