Fix TProfile creation in ROOT monitoring sink when SetDefaultSumw2 is used

When the static function TH1::SetDefaultSumw2 had been called (passing true), Sumw2(true) is automatically called by the constructor of TProfile. This is a problem because in the profiles in Gaudi::Accumulators we do not keep track of the sum of squares of weights and consequently don't set fBinSumw2 of the TProfile, which in turn leads to a self-inconsistent TProfile object. The "fix" is to disable sum of squares explicitly.

This fix is required for the LHCb online monitoring machinery which (in some cases) relies on Gaudi::Histograming::Sink::Root to save histograms.