qemu-io: Use bool for command line flags

We require a C99 compiler; let's use it to express what we
really mean.

(Yes, we now have an instance of 'if (bool + bool + bool > 1)',
which, although semantically valid C, looks ugly; it gets
cleaned up later.)

Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Message-id: 1462677405-4752-4-git-send-email-eblake@redhat.com
Signed-off-by: Max Reitz <mreitz@redhat.com>
