Remove support for service callback plugins

This patch removes the now heavily outdated (and non-working) support
for callback plugins.  I.e. plugins that attach themselves to services
listed in /etc/finit.conf and can be queried to determine if a service
should be started or stopped.

The Finit3 support for adding/removing services at runtime with plain
text *.conf files in /etc/finit.d and `initctl reload`, this old, and
rather cumbersome service callback feature, is not longer supported.

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>

plugin.h

@@ -100,13 +100,6 @@ typedef struct plugin {
 	 * NOTE: Must match cmd for services or inetd plugins! */
 	char *name;
 
-	/* Service callback to be called once per lap of runloop. */
-	struct {
-		int dynamic;      /* Callback wants external events as well. */
-		int dynamic_stop; /* Callback allows dynamic events to stop. */
-		svc_cmd_t (*cb)(svc_t *svc, int event, void *event_arg);
-	} svc;
-
 	/* List of hook callbacks. */
 	struct {
 		void  *arg;      /* Optional argument to callback func. */