[WESTON-INIT] Fix weston.service using root user

FIXME: weston should be run as weston, not as root

recipes-graphics/wayland/weston-init.bbappend

+
+update_file() {
+    if ! grep -q "$1" $3; then
+        bbfatal $1 not found in $3
+    fi
+    sed -i -e "s,$1,$2," $3
+}
+
+do_install:append() {
+    # FIXME: weston should be run as weston, not as root
+    update_file "User=weston" "User=root" ${D}${systemd_system_unitdir}/weston.service
+    update_file "Group=weston" "Group=root" ${D}${systemd_system_unitdir}/weston.service
+}