Add a disk to an instance in config
Add a disk to an instance in config

Implement functions 'AddDisk' and 'AttachInstanceDisk'. The first one
adds a new disk to the config file and the second one attaches a disk to
an instance. A wrapper 'AddInstanceDisk' is provided in order to add a
disk and attach it to an instance at once (because Ganeti doesn't
support dangling disks right now).

Signed-off-by: Ilias Tsitsimpis <7f657306c3c5f1ef1cfa2e11204de3febce40ef6@grnet.gr>
Reviewed-by: Jose A. Lopes <0fb9c4f8511df4ec2ae28af879e9d462f6218a2c@google.com>

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