Makes KeyName an optional parameter
Makes KeyName an optional parameter

If this is left blank, then SSH will be disabled on agents. This
provides an additional level of agent security, and the existing
CloudWatch logs provide a good level of debuggability/diagnostics.

holmesjr/elastic-ci-stack-for-aws,buildkite/elastic-ci-stack-for-aws,holmesjr/elastic-ci-stack-for-aws