manager.c: Fix regression due to using wrong free function.

Commit 424be34563 introduced
a regression by calling ast_free on memory allocated by
realpath. This causes Asterisk to abort when executing this
function. Since the memory is allocated by glibc, it should
be freed using ast_std_free.

Resolves: #513
(cherry picked from commit d6245bcfa3)

main/manager.c

@@ -3763,7 +3763,7 @@ static int restrictedFile(const char *filename)
 {
 	char *stripped_filename;
 	RAII_VAR(char *, path, NULL, ast_free);
-	RAII_VAR(char *, real_path, NULL, ast_free);
+	RAII_VAR(char *, real_path, NULL, ast_std_free);
 
 	if (live_dangerously) {
 		return 0;