If "who ~" is relative clause or interrogative clause

excerpted from Scene 1 of "Betrayal" by Harold Pinter

JERRY : What a funny thing. We were such close friends, weren’t we? Robert and me, even though I haven’t seen him for a few months, but through all those years, all the drinks, all the lunches … we had together, I never even gleaned … I never suspected … that there was anyone else … in his life but you. Never. For example, when you’re with a fellow in a pub, or a restaurant, for example, from time to time he pops out for a ***, you see, who doesn’t, but what I mean is, if he’s making a crafty telephone call, you can sort of sense it, you see, you can sense the pip pip pips. Well, I never did that with Robert. He never made any pip pip telephone calls in any pub I was ever with him in. The funny thing is that it was me who made the pip pip calls?to you, when I left him boozing at the bar. That’s the funny thing.

My Question :
Can you let me know what does "who doesn’t"(highlighted in bold type in the above paragraph) mean?
I wonder whether it is relative clause, whose antecedent is "he," or interrogative clause, which means 'who doesn't pops out for a *** from time to time?'

Thank you in advance.