Update 630_verify_resolv_conf_file.sh

Add #2101 (comment) to the comments
and copy the file verbosely when rear is run in verbose mode.

usr/share/rear/build/GNU/Linux/630_verify_resolv_conf_file.sh

@@ -42,8 +42,14 @@ fi
 if test -h $ROOTFS_DIR/etc/resolv.conf ; then
     rm -f $ROOTFS_DIR/etc/resolv.conf
     if [[ -f /run/systemd/resolve/resolv.conf ]] ; then
-        # ubuntu18.x real resolv.conf file: quick hack on #2018
-        cp /run/systemd/resolve/resolv.conf $ROOTFS_DIR/etc/resolv.conf
+        # For Ubuntu 18.x use a real resolv.conf file: quick hack on #2018
+        # See https://github.com/rear/rear/pull/2101#issuecomment-478496081
+        # for an example what the symlink target /etc/resolv.conf and the files
+        # /lib/systemd/resolv.conf and /run/systemd/resolve/resolv.conf contain.
+        # Basically /etc/resolv.conf and /lib/systemd/resolv.conf contain only
+        # the systemd-resolved stub resolver "nameserver 127.0.0.53" and
+        # only /run/systemd/resolve/resolv.conf contains a real nameserver:
+        cp $v /run/systemd/resolve/resolv.conf $ROOTFS_DIR/etc/resolv.conf
     else
         cp $v /etc/resolv.conf $ROOTFS_DIR/etc/resolv.conf
     fi