Do not increase millisToWait in JobAcquisitionThread

If job acquisiton (or execution) fails, the exception is caught and the wait time to check for jobs is increased by factor 2. This behavior is not ideal since it means that if ever something goes wrong, even if it only goes wrong once, the wait/sleep time is then doubled for the entire life-time of the acqusition thread, i.e. until I shut down Activiti which might not happen for months in production. The behavior above means that if I have four exceptions during job acqusition/execution, I'm at the maximum wait time of 1 minute.

If this increasing wait time is some sort of self-adapting feature, the system should also self-adapt back to the normal state, rather than to remain in the corner it once drifted to, due to some exceptions that might have happened over an interval of several hours/days/weeks.

Suggested fix:
a) Make the factor configurable, rather than hard-coding it to 2. One could then configure the factor to 1 and not have any increase in the wait time ever
b) remove the logic of increasing the wait time since it adds no value, it only adds complexity (my - maybe limited - view on this)

I mean all of this in a very constructive way.