amazon-cloudwatch-agent: onPremise default profile configuration broken

Describe the bug

Commit 6119858864c317ff26f41f576c169148d1250837 changes the config.ModeOnPrem string from onPremise to onPrem, however several programs receive this string as a command-line argument (e.g. config-downloader) from amazon-cloudwatch-agent-ctl and fail to recognize the region or credentials as a consequence. For example, config-downloader takes the string onPremise as its mode flag, which used to compare equal with config.ModeOnPrem, but no longer does after this change, which means GetCredentials no longer sets the credential profile to DEFAULT_PROFILE.

Steps to reproduce

/opt/aws/amazon-cloudwatch-agent/bin/amazon-cloudwatch-agent-ctl -a fetch-config -m onPremise -c file:cloudwatch.json -s where common-config.toml doesn’t contain a credentials block.

What did you expect to see?

I! SDKRegionWithCredsMap region:  us-west-2

or

****** processing amazon-cloudwatch-agent ******
Got Home directory: /root I! Set home dir Linux: /root I! SDKRegionWithCredsMap region: us-west-2 Successfully fetched the config and saved in /opt/aws/amazon-cloudwatch-agent/etc/amazon-cloudwatch-agent.d/file_cloudwatch.json.tmp

and so on, which is the output with 1.247354 or with shared credentials explicitly set.

What did you see instead?

Unable to determine aws-region.

or sometimes

****** processing amazon-cloudwatch-agent ******
2022/09/01 19:21:25 E! Please make sure the credentials and region set correctly on your hosts.

depending on the state of existing configuration on the host.

What version did you use?

v1.247355.0. Confirmed that v1.247354.0 works fine.

Environment

Ubuntu 18.04.6 LTS (Bionic Beaver)

Additional context

I recommend either reverting the change, or a patch like this: (note that anything that specifies mode arguments to the programs that consume this string must be adjusted)

diff --git a/packaging/dependencies/amazon-cloudwatch-agent-ctl b/packaging/dependencies/amazon-cloudwatch-agent-ctl
index 5c5fbcf..1e9c722 100755
--- a/packaging/dependencies/amazon-cloudwatch-agent-ctl
+++ b/packaging/dependencies/amazon-cloudwatch-agent-ctl
@@ -514,7 +514,7 @@ main() {
 
      case "${mode}" in
      ec2) ;;
-     onPremise) ;;
+     onPremise) mode=onPrem ;;
      auto) ;;
      *)
           echo "Invalid mode: ${mode} ${UsageString}" >&2