AthenaMonitoringKernel: always set kAlwaysCreate for lumiblock histograms online

Frank Winklmeierrequested to merge
fwinkl/athena:klbn into 23.0

For the correct functioning of the Gatherer, lumiblock histograms should always be created with the kAlwaysCreate option to ensure they are re-booked on each LB change.

Relates to ADHI-4947.

cc @salnikov

P.S.: Should have really done this a long time ago. I was reminded by @stelzer in !64147 (merged).

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