MH-10034, temporary fix to stop gathering of unused job statistics
MH-10034, changed to a optional configuration
MH-10034, changed default to true
MH-10034, changed default to true
MH-10034, set internal variable to default
Merge branch 'jperrin/t/MH-10034-jobstatistics' into r/1.4.2

MH-10034, temporary fix to stop gathering of unused job statistics.

It introduces an option to disable the gathering of job statistics which
is not used at the moment but will probably be used again in the future.
Disabling it should have a big positive performance impact, especially
at larger Matterhorn clusters.