avoiding duplicated DB-Error in second layer

### Description
o Transaction ID for ontimeinterval
o LM_I for every database operation
o Avoided repeating 'Database Error' in second call-layer

I don't remember in which point of the code, but I think that we set transaction back to "N/A" just before pass control to MHD for reply sending. Should we do the same in this part? I mean, to set "N/A" before sleeping back again.