[stable/grafana] fix servicePort assignment in ingress.yaml (#1598)

Fixes chart deployment.

stable/grafana/Chart.yaml

@@ -1,5 +1,5 @@
 name: grafana
-version: 0.4.1
+version: 0.4.2
 description: The leading tool for querying and visualizing time series and metrics.
 home: https://grafana.net
 icon: https://raw.githubusercontent.com/grafana/grafana/master/public/img/logo_transparent_400x.png

stable/grafana/templates/ingress.yaml

@@ -1,6 +1,6 @@
 {{- if .Values.server.ingress.enabled -}}
 {{- $releaseName := .Release.Name -}}
-{{- $servicePort := .Values.server.httpPort -}}
+{{- $servicePort := .Values.server.service.httpPort -}}
 apiVersion: extensions/v1beta1
 kind: Ingress
 metadata: