I highly doubt that the barman in the pub was Voldemort. Tom the barman had worked in that bar before Tom Riddle even knew he could perform magic! If you reference HBP, in Dumbledore's memory of going to the orphanage to offer Tom a spot at Hogwarts, there is mention of Tom (bar man).

"Dumbledore handed Riddle the envelope containing his list of equipment, and after telling Riddle exactly how to get to the Leaky Cauldron from the orphanage, he said, 'You will be able to see it, although Muggles around you - non-magical people, that is - will not. Ask for Tom the barman - easy enough to remember, as he shares your name-'"

Riddle then reveals his disdain for the ordinary name Tom. I think that we can assume that his revulsion of being considered anything less than special and even moreso, anything that would remind him of his Muggle father, would prevent him from even associating with Tom the barman, let alone possessing such an "ordinary" person.