Before this PR, CLI functions fatal out when encountering error
instead of returning it. Such behavior makes it hard to reuse
the functions nor writing unit tests. This PR aims to make functions
return errors instead of error out.
The utility function GetMetadata uses wrong flag text to get the resource namespace and could cause the wrong results returned from the API server. This PR changes the function signature that allows users to pass in the flag text in order to get the correct value.
