Consistent help messages for all commands

[kensipe]

What type of PR is this?
/component kudoctl
/kind cleanup

What this PR does / why we need it:
Commands previously were inconsistent with usage info... some used the default (like test and get) however several overrode the default help. All the overrides resulted in the help text not be displayed at all. For instance go run cmd/kubectl-kudo/main.go update --help
resulted in:

Update installed KUDO operator with new parameters.

Usage:
  kubectl-kudo update <instance-name> [flags]

Flags:
  -h, --help                    help for update
      --kubeconfig string       Path to your Kubernetes configuration file (default "/Users/kensipe/.kube/config")
      --namespace string        The namespace where the instance you want to upgrade is installed in. (default "default")
  -p, --parameter stringArray   The parameter name and value separated by '='

Now it results in:

go run cmd/kubectl-kudo/main.go update --help
Update installed KUDO operator with new parameters.

Usage:
  kubectl-kudo update <instance-name> [flags]

Examples:

		The update argument must be a name of the instance.

		# Update dev-flink instance with setting parameter param with value value
		kubectl kudo update dev-flink -p param=value

		# Update dev-flink instance in namespace services with setting parameter param with value value
		kubectl kudo update dev-flink -n services -p param=value

Flags:
  -h, --help                    help for update
      --namespace string        The namespace where the instance you want to upgrade is installed in. (default "default")
  -p, --parameter stringArray   The parameter name and value separated by '='

Global Flags:
      --kubeconfig string   Path to your Kubernetes configuration file (default "/Users/kensipe/.kube/config")

Making use of the examples in code. It also has the advantage of showing what the global flags are.

Which issue(s) this PR fixes:
Fixes #

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

NONE

[jbarrick-mesosphere]

/approve

-25, +0, my favorite kind of PR

[kudo-ci]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: jbarrick-mesosphere, kensipe

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[alenkacz]

nice 👏

/lgtm