blockdev: Keep track of monitor-owned BDS

As a side effect, we can now make x-blockdev-del's check whether a BDS
is actually owned by the monitor explicit.

Signed-off-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

stubs/Makefile.objs

@@ -1,5 +1,6 @@
 stub-obj-y += arch-query-cpu-def.o
 stub-obj-y += bdrv-commit-all.o
+stub-obj-y += blockdev-close-all-bdrv-states.o
 stub-obj-y += clock-warp.o
 stub-obj-y += cpu-get-clock.o
 stub-obj-y += cpu-get-icount.o

stubs/blockdev-close-all-bdrv-states.c

@@ -0,0 +1,5 @@
+#include "block/block_int.h"
+
+void blockdev_close_all_bdrv_states(void)
+{
+}