offset management: settings for offset_start(offset::Beginning()) do not correctly retreive the consumer offset

[digikata]

offset_start(Offset::end()) picks the end w/o retrieving the consumer id offset
offset_start(Offset::from_end(1) picks the end - 1 w/o retrieving the consumer id offset

Needs additional test cases

[ajhunyady]

I think that begin() is the only one that works. We should ensure that all other offset flavors work, end(), from_end(), from_beggining(), etc.