The current default allows to lose data very easily: if the dispatcher
fails to send data to the backend (e.g. Gnocchi is down), then the
dispatcher raises and the data are lost for ever. This is completely
unacceptable, and nobody should be able to configure Ceilometer in that
way.
This patch entirely remove that option, and switch the behavior to
something sane.
Change-Id: I45cb3da84eb2a785f46b3ec676c1a052ce999206
40684dafae