Fixed computation of "levels" in EvtStoreSvc

The levels are basically the number of slashes in a path in the store. But EvtStoreSvc was not taking into account the slashes in the rootName, thus having lower numbers.

added bug fix label

approved this merge request

changed milestone to %v36r5

added lhcb-gaudi-head label

assigned to @clemenci

• [2022-03-24 00:04] Validation started with lhcb-gaudi-head#3196
• [2022-03-24 00:34] Validation started with lhcb-run2-gaudi-head#295
• [2022-03-25 00:06] Validation started with lhcb-gaudi-head#3197
• [2022-03-25 00:39] Validation started with lhcb-run2-gaudi-head#296

merged

mentioned in commit d2505f34