[Tamas-Biro1]

This PR fixes the #130

THe problem: static route operator could crash with panic: panic called with nil argument. The reason is that Netlink closes the route update channel on any receive error (e.g. ENOBUFS), so RouteManager.Run() then returned nil, and main.go called panic(nil) with it.

In this PR:

• RouteManager.Run() now subscribes again when Netlink closes the update channel, so the operator keeps running instead of crashing
• Run() returns nil only when stopChan is closed, and returns a wrapped error if the subscription fails
• main.go no longer calls panic(nil):
  • if the route manager exits, the operator panics with the error it returned, or with route manager stopped unexpectedly if it returned nil
  • if the StaticRoute CRD is missing, it panics with CRD not found: staticroutes.static-route.ibm.com
• updated unit tests

[mihivagyok]

/lgtm