iotests: Update 186 after commit ac64273c66ab136c44043259162

iotests: Update 186 after commit ac64273c66ab136c44043259162

Commit ac64273c66ab136c44 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: Alberto Garcia <berto@igalia.com>
Cc: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>