The full log cfn-init.log is not available on CloudWatch

**Required Info:**
- AWS ParallelCluster version: 3.4.1

**Bug description:**
I am not able to reproduce this bug consistently, what happens is the `cfn-init.log` is sometimes split into multiple logs, `cfn-init.log-1` and `cfn-init.log-2` and the logs are spread across these files.

The default cloudwatch agent only uploads the `cfn-init.log` as it's configured to, so we are unable to see the full log without the rest of the files.
This is especially troublesome when the node fails to create, difficult to debug what went wrong without the full information.
It would be nice to have the default cloudwatch agent file updated to have these additional files in cloudwatch should they be split into many parts or make sure splitting of files does not happen.