af-main: ensure socket activation

af-main: ensure socket activation

When installing a widget, the sockets.target
has to be restarted. This commit does it.

AGL-Bug: SPEC-670

Change-Id: I7200749716c57778d165971a5abea27493ce0628
Signed-off-by: José Bollo <jose.bollo@iot.bzh>
Reviewed-on: https://gerrit.automotivelinux.org/gerrit/9793
Tested-by: Jenkins Job builder account <agl-jobbuilder@automotivelinux.org>
ci-image-build: Jenkins Job builder account <agl-jobbuilder@automotivelinux.org>
Reviewed-by: Jan-Simon Moeller <jsmoeller@linuxfoundation.org>