MINOR: actions: add a function returning a service pointer from its name

This function simply calls action_lookup() on the private service_keywords,
to look up a service name. This will be used to detect double registration
of a same service from Lua.

This will be needed by a next patch to fix a bug and will have to be
backported.

(cherry picked from commit 87e539906b13ed1d86684d9d3eab82b550fae02d)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>
diff --git a/src/stream.c b/src/stream.c
index 8d6bdb2..15ea23d 100644
--- a/src/stream.c
+++ b/src/stream.c
@@ -2770,6 +2770,11 @@
 	LIST_ADDQ(&service_keywords, &kw_list->list);
 }
 
+struct action_kw *service_find(const char *kw)
+{
+	return action_lookup(&service_keywords, kw);
+}
+
 /* Lists the known services on <out> */
 void list_services(FILE *out)
 {