Commit ac64273c modified the output of iotest 186, changing
the QOM path of floppy drives from /machine/unattached/device[17] to
/machine/unattached/device[13].

Instead of updating the test output to reflect this change, this patch
adds a new filter that hides all QOM paths from the 'Attached to:'
line of the 'info block' command.
Signed-off-by: NAlberto Garcia <berto@igalia.com>
Cc: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>