qemu_driver: increase recorded counter for disk block stats
qemu_driver: increase recorded counter for disk block stats

Commit <318d807a0bd3372b634d1952b559c5c627ccfa5b> added a fix to skip
most of the block stat code to not log error message for missing storage
sources but forgot to increase the recordnr counter.

Signed-off-by: Pavel Hrdina <d4772d05997b8abf035041e3b4f4996380ea7e7a@redhat.com>
Reviewed-by: Michal Privoznik <83d82aaba2eed257f4814b0c239c260c4caaadf0@redhat.com>

jfehlig/libvirt,jfehlig/libvirt,zippy2/libvirt,nertpinx/libvirt,jfehlig/libvirt,crobinso/libvirt,crobinso/libvirt,zippy2/libvirt,olafhering/libvirt,zippy2/libvirt,libvirt/libvirt,olafhering/libvirt,crobinso/libvirt,libvirt/libvirt,nertpinx/libvirt,crobinso/libvirt,nertpinx/libvirt,libvirt/libvirt,zippy2/libvirt,nertpinx/libvirt,olafhering/libvirt,libvirt/libvirt,jfehlig/libvirt,nertpinx/libvirt,olafhering/libvirt