Add validation for iso_storage_pool in an additional_iso_files block

[mpywell]

Add validation of iso_storage_pool in an additional_iso_files block where an iso_url is specified for upload.

...
  additional_iso_files {
    device           = "ide0"
    iso_url          = "https://fedorapeople.org/groups/virt/virtio-win/direct-downloads/stable-virtio/virtio-win.iso"
    iso_checksum     = "none"
    unmount          = true
  }
...

Packer build runs without iso_storage_pool specified for the above block now output

Error: 1 error(s) occurred:

* when specifying iso_url in an additional_iso_files block, iso_storage_pool must also be specified

  on 197.pkr.hcl line 32:
  (source code not available)

Resolves issue described in #197

[hashicorp-cla]

All committers have signed the CLA.

[lbajolet-hashicorp]

LGTM, thanks for the patch @mpywell!

Hopefully this fixes #197 for everyone.

I'll see to release the plugin early next week, this way the fix will be broadly available.

[BonusPlay]

@lbajolet-hashicorp as far as I can see there hasn't been a single release since this has been merged (v1.1.7 released on Jan 24, while this has been merged on Feb 2). Could we get a release?

[lbajolet-hashicorp]

Hi @BonusPlay,

Looks like I forgot to release it when I said I would, sorry about that.

I'll release a version tomorrow, I've put a note in my calendar so I don't forget, thanks for the reminder!