Skip trace for router healthz endpoint (#1400)

Jaeger preserves the trace data of router healthz endpoints
which is not so helpful for monitoring function metrics and
consumes storage to store such trace data.

This PR uses `GetStartOptions` to examine the request's path and
check if it's a request to healthz endpoint. If yes, skip and not
to trace it.

charts/fission-all/templates/router.yaml

@@ -61,6 +61,8 @@ spec:
             value: {{ .Values.router.useEncodedPath | default false | quote }}
           - name: DEBUG_ENV
             value: {{ .Values.debugEnv | quote }}
+          - name: DISPLAY_ACCESS_LOG
+            value: {{ .Values.router.displayAccessLog | default false | quote }}
 {{- if .Values.analytics }}
           - name: ANALYTICS_URL
             value: "https://g.fission.sh/metrics"