Fix post install script dependency

Fix post install script dependency

 * Since yocto pyro we need to declare PACKAGE_WRITE_DEPS, dependency
   for post install script
   http://www.yoctoproject.org/docs/2.3/mega-manual/mega-manual.html#var-PACKAGE_WRITE_DEPS

 * we alsa need to explicit exit 1 if post script failed

Bug-AGL: SPEC-646
Bug-AGL: SPEC-825

Change-Id: Ic15f8af884895fecacceb9886de5bebe591a2be0
Signed-off-by: Ronan Le Martret <ronan.lemartret@iot.bzh>
Reviewed-on: https://gerrit.automotivelinux.org/gerrit/10883
Reviewed-by: Stéphane Desneux <stephane.desneux@iot.bzh>
Reviewed-by: Thomas Rini <trini@konsulko.com>
Reviewed-by: Jan-Simon Moeller <jsmoeller@linuxfoundation.org>
Tested-by: Jan-Simon Moeller <jsmoeller@linuxfoundation.org>