Replace cfn-hup on compute nodes with systemd timers to signal updates

[hgreebe]

Description of changes

• Changes how compute nodes handle in place updates so that we no longer rely on cfn-hup running on compute nodes.
• Replaces cfn-hup with a systemd timer that periodically checks a file in shared storage and runs an update if that file has been modified with the new cluster config version that has not yet been applied to the compute nodes. This file is updated by the head node when a cluster update occurs in order to signal to the compute nodes to update.
• The check-update.service has a 30 second timeout so that it does not run indefinately if something hangs.
• Revert changes for in_place_update_on_fleet_enabled from: 6eda378#diff-6d6c58cce2dd575c0638ee245d9647b0dfa3cbdef86a136bd816d00538529fb4

Tests

• Created unit tests to cover the systemd timer and service as well as new update logic
• Ran all the update integ tests

References

• PR to remove validator test for in_place_update_true chef attribute: Remove in_place_update_true chef attribute from tests aws-parallelcluster#7156

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