KUBERNETES_NAMESPACE_NAME_REGEX does not support '*'

[munnerz]

Additional environment details (Operating System, Cloud provider, etc):
Kubernetes

Steps to reproduce the issue:

1. Attempt to run docker-dd-agent with KUBERNETES_NAMESPACE_NAME_REGEX set to '.*'

Describe the results you received:

• Observe /entrypoint.sh: 66: [: .: unexpected operator in logs
• The namespace REGEX is not written to disk

Describe the results you expected:

• dd-agent should watch all namespaces for Kubernetes events

Additional information you deem important (e.g. issue happens only occasionally):

This appears to happen as the entrypoint script does not quote values when checking if they are set (see: https://github.com/DataDog/docker-dd-agent/blob/master/entrypoint.sh#L58)

As a temporary workaround, I replaced .* with .+, which does solve the issue as + is not evaluated by the shell.

[cknowles]

Hit this as well but used a different workaround of double quoted single quotes.