MEDIUM: spoe: Directly xfer NOTIFY frame when SPOE applet is created

MEDIUM: spoe: Directly xfer NOTIFY frame when SPOE applet is created

Instead of using a buffer from the SPOE filter to store the NOTIFY frame, to
copy it in a trash buffer in the SPOE applet to add meta-data and then tranfer
it to the channel, the original buffer is directly transfered to the channel
during the SPOE applet creation.

The SPOE applet is thus simplied, the I/O handler is now only responsible to
retrieve the ACK reply.

The related issue is #2502.