status: Display number of currently connected clients, and whether new clients are allowed

These will be useful for migration status monitoring - replaces "is pass == 7?"

src/status.c

@@ -12,6 +12,9 @@ struct status * status_create( struct server * serve )
 	status->size = serve->size;
 	status->has_control = serve->success;
 
+	status->clients_allowed = serve->allow_new_clients;
+	status->num_clients = server_count_clients( serve );
+
 	server_lock_start_mirror( serve );
 
 	status->is_mirroring = NULL != serve->mirror;
@@ -51,6 +54,8 @@ int status_write( struct status * status, int fd )
 	PRINT_INT( pid );
 	PRINT_UINT64( size );
 	PRINT_BOOL( is_mirroring );
+	PRINT_BOOL( clients_allowed );
+	PRINT_INT( num_clients );
 	PRINT_BOOL( has_control );
 
 	if ( status->is_mirroring ) {

src/status.h

@@ -30,6 +30,14 @@
  * 	If the server is started in "serve" mode, this will never be
  * 	false.
  *
+ * clients_allowed:
+ *   This will be false if the server is not currently allowing new
+ *   connections, for instance, if we're in the migration endgame.
+ *
+ * num_clients:
+ *   This tells us how many clients are currently running. If we're in the
+ *   migration endgame, it should be 0
+ *
  * is_migrating:
  * 	This will be false when the server is started in either "listen"
  * 	or "serve" mode.  It will become true when a server in "serve"
@@ -73,6 +81,8 @@ struct status {
 	pid_t pid;
 	uint64_t size;
 	int has_control;
+	int clients_allowed;
+	int num_clients;
 	int is_mirroring;
 	int migration_pass;
 	uint64_t pass_dirty_bytes;