blkdebug: Simplify and improve filename generation

Instead of actually recreating the options from scratch, just reuse the
options given for creating the BDS, which are the configuration file
name and additional options. In case there are no additional options we
can thus create a plain filename.

This obviously results in a different output for qemu-iotest 099 which
exactly tests this filename generation. Fix it up as well.

Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-id: 1415697825-26678-2-git-send-email-mreitz@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
iotests: Plain blkdebug filename generation

Add one test whether blkdebug is able to generate a plain filename if
given a configuration file and a file to be tested only; and add another
test whether blkdebug is able to do the same without being given a
configuration file.

Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-id: 1415697825-26678-3-git-send-email-mreitz@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>