keyutils: fix deprecated function usage

Signed-off-by: Rosen Penev <rosenp@gmail.com>

libs/keyutils/patches/020-rindex.patch

@@ -0,0 +1,17 @@
+--- a/key.dns_resolver.c
++++ b/key.dns_resolver.c
+@@ -529,12 +529,12 @@ int main(int argc, char *argv[])
+ 	keyend = buf + ktlen + 1;
+ 
+ 	/* the actual key description follows the last semicolon */
+-	keyend = rindex(keyend, ';');
++	keyend = strrchr(keyend, ';');
+ 	if (!keyend)
+ 		error("Invalid key description: %s", buf);
+ 	keyend++;
+ 
+-	name = index(keyend, ':');
++	name = strchr(keyend, ':');
+ 	if (!name)
+ 		dns_query_a_or_aaaa(keyend, callout_info);
+