block/raw-posix: Use raw_normalize_devicepath()

The filename given to qemu_open() in block/raw-posix.c should generally
have been processed by raw_normalize_devicepath(); unless we are only
probing (in which case the caller often checks whether the file is a
block device or not, and this property will be changed by
raw_normalize_devicepath() on NetBSD) or it is about a deprecated device
(i.e. floppy).

Signed-off-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
