block: fix NetBSD qemu-iotests failure

block: fix NetBSD qemu-iotests failure

Opening a block device on NetBSD has an additional step compared to other OSes,
corresponding to raw_normalize_devicepath.  The error message in that function
is slightly different from that in raw_open_common and this was causing spurious
failures in qemu-iotests.  However, in general it is not important to know what
exact step was failing, for example in the qemu-iotests case the error message
contains the fairly unequivocal "No such file or directory" text from strerror.
We can thus fix the failures by standardizing on a single error message for
both raw_open_common and raw_normalize_devicepath; in fact, we can even
use error_setg_file_open to make sure the error message is the same as in
the rest of QEMU.

Message-Id: <20190725095920[email protected]>
Tested-by: Thomas Huth <[email protected]>
Signed-off-by: Paolo Bonzini <[email protected]>
Reviewed-by: Philippe Mathieu-Daudé <[email protected]>
Signed-off-by: Thomas Huth <[email protected]>