After SERVER-46893, there is special handling for isMaster commands  when a node is removed. We should add a unit test for the following case:

• isMaster request during quiesce mode in REMOVED state

(There is no need to test entering quiesce mode from the REMOVED state or test the interaction of quiesce mode and the STARTUP state, since we only enter quiesce mode if we're in state SECONDARY. There is no need to test the behavior of waiting isMaster requests during quiesce mode, since isMaster requests always return immediately during quiesce mode.)