kiali: Jaeger URL configuration problems

Describe the bug External Jaeger URL is used by Kiali for internal requests, which is causing problem if for example AWS ELB is used for Jaeger (Host DNS will not be resolved from pod). So basically there are two situations possible and both of them has problems.

Situation 1 (jaeger url config is set to Extrernal URL (AWS ELB)):

external_services:
      tracing:
        namespace: istio-system
        service: jaeger-tracing-query
        # No ability to set external URL here, because it also will be used for internal calls from Kiali pod, which could be not possible if  for example ELB is used.
        url: https://numbrs-jaeger-sandbox.cwc.io/jaeger

Situation 2 (Internal Jaeger URL is used):

external_services:
      tracing:
        namespace: istio-system
        service: jaeger-tracing-query
        # No ability to set external URL here, because it also will be used for internal calls from Kiali pod, which could be not possible if  for example ELB is used.
        url: http://jaeger-tracing-query.istio-system.svc.cluster.local:16686/jaeger

So in Situation 2 redirection to Jaeger UI will not work, because Internal cluster URL is used.

Additional information

I have made some additional digging and I think that the fast fix could be pretty simple, this if block should be deleted: jaeger.go So internal Jaeger URL will be discovered automatically by service, namespace, port configuration from configs and path (if it configured) from External URL.

The other way to fix this is to use the same strategy as in Grafana integration configurations, where internal and external URL could be declared separately and transparent.

external_services:
  grafana:
        in_cluster_url: http://grafana.monitoring.svc.cluster.local:3000
        url: https://grafana-sandbox.cwc.io

Versions used Kiali: v1.4.0 (also tested with v1.5.0-snapshot.1) Istio: v1.2.2 (with custom ConfigMap for Kiali to support latest Kiali configurations) Kubernetes flavour and version: (e.g. OpenShift Origin 3.9) raw k8s v1.11.7

To Reproduce Steps to reproduce the behavior:

1. Set external Jaeger URL that could be accessible from outside the cluster, in our case through AWS ELB (E.g. https://external-jaeger.test.com/jaeger)
2. Set jaeger.namespace and jaeger.service for Internal URL discovery.
3. Login to Kiali.
4. See error and tracing integration is disabled.

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If in step one we will set internal URL (E.g http://jaeger-query.istio-system.svc.cluster.local:16686/jaeger) there will not be error in Kiali but redirection to Jaeger will not work (E.g. Click on Distributed Tracing button on UI), which is expected.

Expected behavior Both redirection to Jaeger UI and internal Kiali’s requests to Jaeger api works.