HACK: Add amdiskflush application to transform a holding disk into a vtape

[opoplawski]

This allows you to dump to a holding disk with out a "tape" with:

/usr/sbin/amdump --no-taper -o maxdumpsize=$dumpsize -o tapetype:DISK:length=$disksize $config

and then turn that into a vtape with:

/usr/sbin/amdiskflush $config

This allows you to have parallel dumps to disk without duplicating writing that data to disk.

This is quite the hack, but works we for us. Perhaps something like this could be integrated into amanda properly to achieve the same effect.