ctrl_connection: Initialize write_queue.bfd.fd to -1 during allocation

Otherwise fd is set to 0 by default, let's avoid accidentally closing
it if something goes wrong.

Change-Id: I98f744d2880fbb883719cdf1d3eb31f2b22a13b6
diff --git a/src/ctrl/control_if.c b/src/ctrl/control_if.c
index 9e3e3a9..5eb81c7 100644
--- a/src/ctrl/control_if.c
+++ b/src/ctrl/control_if.c
@@ -514,6 +514,7 @@
 	INIT_LLIST_HEAD(&ccon->def_cmds);
 
 	ccon->write_queue.bfd.data = data;
+	ccon->write_queue.bfd.fd = -1;
 	ccon->write_queue.write_cb = control_write_cb;
 	ccon->write_queue.read_cb = handle_control_read;