Fix script to look at just the id

[tchinmai7]

General:

• [ ] Have you removed all sensitive information, including but not limited to access keys and passwords?
• [ ] Have you checked to ensure there aren't other open or closed Pull Requests for the same bug/feature/question? The get-linode-id script can produce a mangled linode-id when there's a tag with a id in there. For example with a metadata response like this

  backups.enabled: true
  backups.status: pending
  host_uuid: 2d56ceffafec9f76be86e1d2d1dd37ec2204b28f
  id: 60586846
  label: jkvbpzyzqaa9pj8ix-master-0
  region: us-ord
  specs.disk: 163840
  specs.gpus: 0
  specs.memory: 8192
  specs.transfer: 5000
  specs.vcpus: 4
  tags: cluster:kpp-api-single
  tags: clusterUid:jkvbpzyzqaa9pj8ix
  tags: prov-from:mgmt-cluster.akamai-kpp.com
  type: g6-standard-4

  the script ends up with

  60586846clusterUid:jkvbpzyzqaa9pj8i

This fixes it by explictly asking for json and looking only at the "id" param.

Pull Request Guidelines:

1. [x] Does your submission pass tests?
2. [ ] Have you added tests?
3. [x] Are you addressing a single feature in this PR?
4. [x] Are your commits atomic, addressing one change per commit?
5. [x] Are you following the conventions of the language?
6. [x] Have you saved your large formatting changes for a different PR, so we can focus on your work?
7. [x] Have you explained your rationale for why this feature is needed?
8. [x] Have you linked your PR to an open issue