Escape the ? expression in sed

Fixes #817, fixes #820

stage2/01-sys-tweaks/01-run.sh

@@ -71,8 +71,8 @@ on_chroot << EOF
 DEBIAN_FRONTEND=noninteractive dpkg-reconfigure keyboard-configuration
 EOF
 
-sed -i 's/^#?Storage=.*/Storage=volatile/' "${ROOTFS_DIR}/etc/systemd/journald.conf"
+sed -i 's/^#\?Storage=.*/Storage=volatile/' "${ROOTFS_DIR}/etc/systemd/journald.conf"
 
 if [ -e "${ROOTFS_DIR}/etc/avahi/avahi-daemon.conf" ]; then
-  sed -i 's/^#?publish-workstation=.*/publish-workstation=yes/' "${ROOTFS_DIR}/etc/avahi/avahi-daemon.conf"
+  sed -i 's/^#\?publish-workstation=.*/publish-workstation=yes/' "${ROOTFS_DIR}/etc/avahi/avahi-daemon.conf"
 fi