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.

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