Fix unintended fallthrough in CbmTrdDigi SetTime

Original behavior before last change was always set time in FASP mode.
After last change is became always set time in SPADIC mode. This probably went unnoticed because the default simulation geometry has only SPADIC-like chambers.
This MR restore the intended dual case usage

Of interest to: @v.friese @a.bercuci

Dear @praisig,

you have been identified as code owner of at least one file which was changed with this merge request.

Please check the changes and approve them or request changes.

added CodeOwners label

approved this merge request

Looks good to me.

merged

Hi Pierre,

We had some problems trying to simulate the TRD2D due to this bug. I was also preparing the same fix but thx that you pushed it faster to the master. Alex