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/af_unix.cc

@@ -151,9 +151,11 @@ int unix_rule::expand_variables(void)
 	error = expand_entry_variables(&addr);
 	if (error)
 		return error;
+	filter_slashes(addr);
 	error = expand_entry_variables(&peer_addr);
 	if (error)
 		return error;
+	filter_slashes(peer_addr);
 
 	return 0;
 }