iotests: remove qemu_io_silent() and qemu_io_silent_check().

iotests: remove qemu_io_silent() and qemu_io_silent_check().

Like qemu-img, qemu-io returning 0 should be the norm and not the
exception. Remove all calls to qemu_io_silent that just assert the
return code is zero (That's every last call, as it turns out), and
replace them with a normal qemu_io() call.

qemu_io_silent_check() appeared to have been unused already.

Signed-off-by: John Snow <jsnow@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Hanna Reitz <hreitz@redhat.com>
Message-Id: <20220418211504.943969-12-jsnow@redhat.com>
Signed-off-by: Hanna Reitz <hreitz@redhat.com>