Missing Link Cost validation and defaulting logic

[c-kruse]

Describe the bug
The skupper Link resource's spec.cost field is an optional integer that is today mapped directly into a skupper-router connector configuration entity. In the router, a connector's cost must be an integer greater than 0. This gap leaves us open to two problems.

• When cost is omitted or set to 0 the skupper-router defaults it to 1. The kube-adaptor detects drift between desired and actual connector configuration and recreates the connector - churning connections.
• When cost is explicitly set to a negative number there are two failure modes:
  • The management agent of a RUNNING skupper-router defaults cost to 1 and the same kube-adaptor behavior above churns connector configuration.
  • The router fails to start loading the configuration from disk with stricter validations. Invalid cost (-1) specified. Minimum value for cost is 1 and maximum value is 2147483647

How To Reproduce

• Generate a link or token with cost unset. This is the default behavior using the skupper ansible token module.
• Apply this link and watch the router and kube-adaptor logs for evidence of this pattern
• Update the link cost to a negative number
• Watch the router pod logs for continued evidence of connector config churn
• Restart the router deployment and see a CrashBackOff Loop.

Environment
Kube

Versions: mainly v2-dev - an unrelased change makes Cost=0 unstable.

Expected behavior
TBD

• A Link with no cost set, or cost=0 resolves to a stable router connector with cost=1
• A link with cost set less than 0 is put in an error state, is removed from router configuration and the CONFIGURED status condition reflects that it is not configured.