feat(aws garbage collector) skips snapshots in use

[jayfranco999]

Related to jenkins-infra/helpdesk#4355

As per jenkins-infra/helpdesk#4355 (comment)

This PR enables debugging to skip snapshots in use

[jayfranco999]

Update:

aws_snapshots.sh now filters the snapshots using ec2 describe-images command and skips the deletion process if used by any instance

Tested locally and successfully:

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== Checking if snapshot snap-0de2d342849db0f36 is in use...
+ aws ec2 describe-images --region=us-east-2 --profile terraform-admin --filters Name=block-device-mapping.snapshot-id,Values=snap-0de2d342849db0f36 --query 'Images[*].ImageId' --output text
+ grep -q .
++ aws ec2 describe-images --region=us-east-2 --profile terraform-admin --filters Name=block-device-mapping.snapshot-id,Values=snap-0de2d342849db0f36 --query 'Images[*].ImageId' --output text
+ ami_ids=ami-08bcac05a9c36fa78
+ echo '[INFO] Snapshot snap-0de2d342849db0f36 is in use by the following AMI(s): ami-08bcac05a9c36fa78. Skipping.'
[INFO] Snapshot snap-0de2d342849db0f36 is in use by the following AMI(s): ami-08bcac05a9c36fa78. Skipping.
+ for snapshot_id in '${snapshot_ids}'
+ echo '== Checking if snapshot snap-02e06c3062de44a91 is in use...'
== Checking if snapshot snap-02e06c3062de44a91 is in use...
+ aws ec2 describe-images --region=us-east-2 --profile terraform-admin --filters Name=block-device-mapping.snapshot-id,Values=snap-02e06c3062de44a91 --query 'Images[*].ImageId' --output text
+ grep -q .
++ aws ec2 describe-images --region=us-east-2 --profile terraform-admin --filters Name=block-device-mapping.snapshot-id,Values=snap-02e06c3062de44a91 --query 'Images[*].ImageId' --output text
+ ami_ids=ami-08fb812ab1ce90606
+ echo '[INFO] Snapshot snap-02e06c3062de44a91 is in use by the following AMI(s): ami-08fb812ab1ce90606. Skipping.'
[INFO] Snapshot snap-02e06c3062de44a91 is in use by the following AMI(s): ami-08fb812ab1ce90606. Skipping.
+ echo '== AWS Packer Cleanup SNAPSHOTS finished.'
== AWS Packer Cleanup SNAPSHOTS finished.