The Collaborative International Dictionary of English v.0.48:
Timeserver \Time"serv`er\, n. One who adapts his opinions and manners to the times; one who obsequiously compiles with the ruling power; -- now used only in a bad sense. [1913 Webster]WordNet (r) 3.0 (2006):
timeserver n 1: one who conforms to current ways and opinions for personal advantage