Fix SetStatusReturnLevel when servo is set < 2
Fix SetStatusReturnLevel when servo is set < 2

This method previously hung if called when the status return level of a
servo was set to zero or one, because it used the locally-stored value
of the return level to determine whether to wait for a response or not,
rather than the value being set -- which, if set successfully,
determines the verbosity of the response to that command.

adammck/dynamixel