Handle error during run-agl-postinsts

Handle error during run-agl-postinsts

 * do not remove post install script if failed

Bug-AGL: SPEC-700

Change-Id: I1b45670ecbe3915a69cfa659031ac877eb794571
Signed-off-by: Ronan Le Martret <ronan.lemartret@iot.bzh>
Reviewed-on: https://gerrit.automotivelinux.org/gerrit/10025
Reviewed-by: José Bollo <jobol@nonadev.net>
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>
(cherry picked from commit 0c28379c6d8ab33f3c902b6617503ca634b8c90e)
Reviewed-on: https://gerrit.automotivelinux.org/gerrit/10091