IMAP: Do not load inbox spawner if auto-connect is on.

If auto-connect is off, we'll rely on the old "page load to spawn inbox
check" method.

If auto-connect is on, we're going to be using the auto-connect admin option
to manually ping the IMAP inbox from the admin settings page.  This will
prevent duplicate IMAP connections from occurring and will also workaround
using wp_remote_post() to spawn the inbox check.  This logic will be
added in subsequent commits.

See #40.

includes/bp-rbe-hooks.php

@@ -14,8 +14,12 @@
 
 	// imap mode hooks
 	if ( ! bp_rbe_is_inbound() ) {
-		// cron - only run on the root blog and if WP cron is not active
-		if ( bp_is_root_blog() && ! defined( 'DOING_CRON' ) ) {
+		/*
+		 * Cron - only run if:
+		 *  - We're the root blog and if WP cron is not active
+		 *  - And if auto-connect is off.
+		 */
+		if ( bp_is_root_blog() && ! defined( 'DOING_CRON' ) && 1 !== (int) bp_rbe_get_setting( 'keepaliveauto' ) ) {
 			add_action( 'init', 'bp_rbe_should_connect',     20 );
 			add_action( 'init', 'bp_rbe_run_inbox_listener', 999 );
 		}