I haven't heard of this. Something you might be thinking of:

Visiting revolutionary Petrograd, John Reed recorded the following in Ten Days that Shook the World:

The waiters and hotel servants were organised, and refused tips. On the walls of restaurants they put up signs which read, “No tips taken here–” or, “Just because a man has to make his living waiting on table is no reason to insult him by offering him a tip!”

Privately owned restaurants certainly existed under the NEP (1920-1928). They were mostly nationalized and placed under the control of collectives in the early thirties, but not closed down. From 1930 to 1934 they were reserved for foreigners as the USSR courted foreign capital.

p.93 Fitzpatrick, Sheila. Everyday Stalinism.