Revert "GWRequestHandler: fix setting of ID to GWGatewayAccepted"
Revert "GWRequestHandler: fix setting of ID to GWGatewayAccepted"

This reverts commit a37fd4042e3150f7e6175e0cc21e236c40f187f6.

The message GWGatewayRegister does not contain any ID. Thus, it
is not possible to derive ID of the GWGatewayAccepted message
and the reverted code thus fails on an exception "Cannot convert
empty value" coming from serialization.

Signed-off-by: Jan Viktorin <3eab6ac54c005c4408f608556a6663b7f2abede7@fit.vutbr.cz>

BeeeOn/server,BeeeOn/server,BeeeOn/server,BeeeOn/server