bind mount /etc/resolv.conf instead of overwriting/removing

Signed-off-by: Steven Armstrong <steven@icarus.ethz.ch>

cdist/conf/type/__chroot_mount/gencode-remote

@@ -42,7 +42,6 @@ mountpoint -q "${chroot}/dev/pts" \
 mountpoint -q "${chroot}/tmp" \
    || mount -t tmpfs -o mode=1777,strictatime,nodev,nosuid tmpfs "${chroot}/tmp"
 
-if [ ! -f "${chroot}/etc/resolv.conf" ]; then
-   cp /etc/resolv.conf "${chroot}/etc/"
-fi
+mountpoint -q "${chroot}/etc/resolv.conf" \
+   || mount --bind -o ro /etc/resolv.conf "${chroot}/etc/resolv.conf"
 DONE

cdist/conf/type/__chroot_umount/gencode-remote

@@ -26,7 +26,9 @@ umount -l "${chroot}/dev/pts"
 umount -l "${chroot}/dev"
 umount -l "${chroot}/sys"
 umount -l "${chroot}/proc"
-rm -f "${chroot}/etc/resolv.conf"
+if mountpoint -q "${chroot}/etc/resolv.conf"; then
+   umount "${chroot}/etc/resolv.conf"
+fi
 if [ -d "${chroot}/etc/resolvconf/resolv.conf.d" ]; then
    # ensure /etc/resolvconf/resolv.conf.d/tail is not linked to \
    # e.g. /etc/resolvconf/resolv.conf.d/original