parser: Fix expansion of variables in unix rules addr= conditional

The parser is not treating unix addr as a path and filtering slashes
after variable expansion. This can lead to errors where

@{foo}=/a/
unix bind addr=@{foo}/bar,

will always fail because addr is being matched as /a//bar instead of
/a/bar.

MR: https://gitlab.com/apparmor/apparmor/-/merge_requests/607
Fixes: https://bugs.launchpad.net/apparmor/+bug/1856738
Signed-off-by: John Johansen <john.johansen@canonical.com>
(cherry picked from commit 6af05006d9)

parser/parser_regex.c

@@ -47,7 +47,7 @@ enum error_type {
  * that's a distinct namespace in linux) and trailing slashes.
  * NOTE: modifies in place the contents of the path argument */
 
-static void filter_slashes(char *path)
+void filter_slashes(char *path)
 {
 	char *sptr, *dptr;
 	BOOL seen_slash = 0;