CLEANUP: acl: remove obsolete test in parse_acl_expr()

The ACL keyword returned by find_acl_kw() is checked for having a
valid ->parse() function. This dates back 2007 when ACLs were reworked
in order to differenciate old and new keywords. This check is
inappropriate and confusing since all keywords have a parser now.
diff --git a/src/acl.c b/src/acl.c
index b04c9df..abfd04c 100644
--- a/src/acl.c
+++ b/src/acl.c
@@ -156,7 +156,7 @@
 	al->conv = NULL;
 
 	aclkw = find_acl_kw(args[0]);
-	if (aclkw && aclkw->parse) {
+	if (aclkw) {
 		/* OK we have a real ACL keyword */
 
 		/* build new sample expression for this ACL */