rules_generator: fix write_cd_rules when similar names exist in the root directory

The argument to find_all_rules must be quoted or it will be subject to
shell expansion, which will happen if in the root directory there are
mount points with the same base name.
See http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=407738 for details.

extras/rule_generator/write_cd_rules

@@ -16,7 +16,7 @@ RULES_FILE="/etc/udev/rules.d/70-persistent-cd.rules"
 . /lib/udev/rule_generator.functions
 
 find_next_available() {
-	raw_find_next_available "$(find_all_rules 'SYMLINK+=' $1)"
+	raw_find_next_available "$(find_all_rules 'SYMLINK+=' "$1")"
 }
 
 write_rule() {