generator.c: systemd-fsck-root.service conflict with shutdown.target

Otherwise a "reboot" or "poweroff" in the initramfs will have to wait
until systemd-fsck-root.service has completed, which might never happen
if the root device never shows up.

src/shared/generator.c

@@ -105,6 +105,7 @@ static int write_fsck_sysroot_service(const char *dir, const char *what) {
                 "BindsTo=%3$s\n"
                 "After=initrd-root-device.target local-fs-pre.target %3$s\n"
                 "Before=shutdown.target\n"
+                "Conflicts=shutdown.target\n"
                 "\n"
                 "[Service]\n"
                 "Type=oneshot\n"