sdbusplus: Move callback instead of copy

We always want to instantiate these a single time, so we can move them.
In the future, the callback_t may chnage to a move only type so we can
support it this way.

Change-Id: I839298f43df108fd9d282fb4e4390e2d32ac3e78
Signed-off-by: William A. Kennington III <wak@google.com>
1 file changed