You can take a very thin steel wire in a pair of vise grip pliers,, heat it up with a sig lighter or over a gas stove, has to be almost but not quite red hot. slide between the servo case and foam,, it will melt the foam right away from the servo/glue,, if glue is under the servo too, you have to bend the wire and twist it under the servo also.

Don't let is linger against the foam to much, and be careful around the servo wire, move quickly, you don't want to melt away too much foam, just enough to loosen up the servo

good luck