af-binder: Make weak ws-client by default (to be fixed)

af-binder: Make weak ws-client by default (to be fixed)

The case of unicens service that can be here or not creates
problem to the binding 4a when the service is not here.
This commits makes the requirement of ws-client
socket optional. This unblocks the situation but need to
be fixed later, for example, by introducing an explicit
weak requirement.

Bug-AGL: SPEC-1151

Change-Id: If935974eb5eeef1238e835ab4b0a46011bfb51b4
Signed-off-by: José Bollo <jose.bollo@iot.bzh>
Reviewed-on: https://gerrit.automotivelinux.org/gerrit/12323
Tested-by: Jenkins Job builder account <agl-jobbuilder@automotivelinux.org>
ci-image-build: Jenkins Job builder account <agl-jobbuilder@automotivelinux.org>
Reviewed-by: Stéphane Desneux <stephane.desneux@iot.bzh>
Reviewed-by: Jan-Simon Moeller <jsmoeller@linuxfoundation.org>