[ros] fix get_time to properly use simulated timestamp

Any particular reason why this was not enabled yet? (Except that it was multiplied by 1000 instead of divided...?)

Seems to work properly here...

Also is there any specific reason why the timestamp is in milliseconds instead of seconds? Seems that when the timestamp is created, the time in sec is multiplied by 1000 to get ms and everywhere just converted to seconds again later...