Fix xmldoc memory leak

This fixes a single-attribute memory leak that was occurring when the
"required" attribute was not true.

(closes issue ASTERISK-22249)
Reported by: Corey Farrell
Tested by: Corey Farrell
Patches:
    xmldoc-free_attr_required.patch uploaded by Corey Farrell
........

Merged revisions 397064 from http://svn.asterisk.org/svn/asterisk/branches/1.8


git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/11@397067 65c4cc65-6c06-0410-ace0-fbb531ad65f3

main/xmldoc.c

@@ -759,6 +759,7 @@ static char *xmldoc_get_syntax_fun(struct ast_xml_node *rootnode, const char *ro
 				if ((paramtype = ast_xml_get_attribute(node, "required"))) {
 					if (!ast_true(paramtype)) {
 						optmidnode = 1;
+						ast_xml_free_attr(paramtype);
 						break;
 					}
 					ast_xml_free_attr(paramtype);