Add a support function to objects.Disk
Add a support function to objects.Disk

This patch adds a function returning the device path if it is computable
from the disk object (and we don't need to instantiate a bdev object on
the target node in order to compute this). Only LVs support this.

Reviewed-by: imsnah


yiannist/ganeti,mbakke/ganeti,leshchevds/ganeti,dimara/ganeti,apyrgio/snf-ganeti,andir/ganeti,ganeti/ganeti,apyrgio/ganeti,apyrgio/ganeti,bitemyapp/ganeti,grnet/snf-ganeti,andir/ganeti,ganeti-github-testing/ganeti-test-1,mbakke/ganeti,bitemyapp/ganeti,andir/ganeti,yiannist/ganeti,ganeti/ganeti,yiannist/ganeti,ganeti/ganeti,onponomarev/ganeti,leshchevds/ganeti,grnet/snf-ganeti,dimara/ganeti,leshchevds/ganeti,mbakke/ganeti,apyrgio/snf-ganeti,ganeti-github-testing/ganeti-test-1,onponomarev/ganeti