afb-config: Increase the default timeout of sessions

The management of sessions is not very well understood
actually. People are using it without refreshing the token.
This has the effect that the binder closes sessions
after one hour.

So no demo can run more than one hour!

Increasing the timeout to more than one year will
solve the demo problem but will not fully solve the
overall problem.

Bug-AGL: SPEC-1296
Bug-AGL: SPEC-1293

Change-Id: I502a45e3c94f0c4633a80b68619a6e608ad36e7a
Signed-off-by: José Bollo <jose.bollo@iot.bzh>