Remove forthcoming disks on downgrade
Remove forthcoming disks on downgrade

Forthcoming disks were newly introduced in Ganeti 2.14, hence
remove them on downgrade. Also remove them from the disks entry
of all (not forthcoming, and hence not removed anyway) instances.
Note that nothing has to be changed in the physical world, as
forthcoming disks are not yet created.

Signed-off-by: Klaus Aehlig <4ce51de36d9068cd7db2eec1151e0f3f95419008@google.com>
Reviewed-by: Niklas Hambuechen <98215d3a72cb13cc9c9956528e50119ca7d1fb8b@google.com>

mbakke/ganeti,ganeti/ganeti,andir/ganeti,leshchevds/ganeti,ganeti/ganeti,onponomarev/ganeti,dimara/ganeti,mbakke/ganeti,grnet/snf-ganeti,andir/ganeti,leshchevds/ganeti,apyrgio/ganeti,andir/ganeti,yiannist/ganeti,yiannist/ganeti,dimara/ganeti,leshchevds/ganeti,apyrgio/ganeti,mbakke/ganeti,grnet/snf-ganeti,yiannist/ganeti,onponomarev/ganeti,ganeti/ganeti,bitemyapp/ganeti,bitemyapp/ganeti