WMS Monitoring: same selection but different grouping leads to different plot shapes

[chaen]

What I reported in #6386 seems to be true for WMS History as well.

The same plot, when grouped by Site or jobType gives very different plots

[EwoudK]

I looked into this issue last week (on DIRAC certification instance) and saw that the site tag 'Multiple' did not get scaled correctly in DIRAC. In ES, the largest spikes is of size 1 after scaling (timestamps are per day, but indices are updated every 15m -> sum of jobs / 4 / 24). However, in DIRAC, it seems that this rescaling is not done. Unfortunately, I rechecked today but I could not find the data anymore.