collector: Allows to requeue a sample

This change allows to choice the behavior when the dispatcher method
fail.

Now we can requeue on the messaging bus the sample by setting:

[collector]
requeue_sample_on_dispatcher_error=True

This only works when the sample have been publisher with the notifier://

DocImpact
Change-Id: I4a2ad60613aa7ac2c7e90996821be0a4fc018ccf
Merge "collector: Allows to requeue a sample"