Use exact match to find context from API server (#750)

Currently, if you have two contexts:
- my-cluster-dev
- my-cluster
and you try to apply to `my-cluster`, it will match the first one

pkg/kubernetes/client/context.go

@@ -135,7 +135,8 @@ func ContextFromIP(apiServer string) (*Cluster, *Context, error) {
 		return nil, nil, err
 	}
 
-	err = find(contexts, "context.cluster", cluster.Name, &context)
+	// find the context that uses the cluster, it should be an exact match
+	err = find(contexts, "context.cluster", fmt.Sprintf("^%s$", cluster.Name), &context)
 	if err == ErrorNoMatch {
 		return nil, nil, ErrorNoContext(cluster.Name)
 	} else if err != nil {