(prometheus) fix prometheus link (#5074)

public/app/plugins/datasource/prometheus/datasource.ts

@@ -43,7 +43,7 @@ export function PrometheusDatasource(instanceSettings, $q, backendSrv, templateS
     return value.replace(/[\\^$*+?.()|[\]{}]/g, '\\\\$&');
   }
 
-  function interpolateQueryExpr(value, variable, defaultFormatFn) {
+  this.interpolateQueryExpr = function(value, variable, defaultFormatFn) {
     // if no multi or include all do not regexEscape
     if (!variable.multi && !variable.includeAll) {
       return value;
@@ -59,6 +59,7 @@ export function PrometheusDatasource(instanceSettings, $q, backendSrv, templateS
 
   // Called once per panel (graph)
   this.query = function(options) {
+    var self = this;
     var start = getPrometheusTime(options.range.from, false);
     var end = getPrometheusTime(options.range.to, true);
 
@@ -73,7 +74,7 @@ export function PrometheusDatasource(instanceSettings, $q, backendSrv, templateS
       activeTargets.push(target);
 
       var query: any = {};
-      query.expr = templateSrv.replace(target.expr, options.scopedVars, interpolateQueryExpr);
+      query.expr = templateSrv.replace(target.expr, options.scopedVars, self.interpolateQueryExpr);
 
       var interval = target.interval || options.interval;
       var intervalFactor = target.intervalFactor || 1;
@@ -99,7 +100,6 @@ export function PrometheusDatasource(instanceSettings, $q, backendSrv, templateS
       return this.performTimeSeriesQuery(query, start, end);
     }, this));
 
-    var self = this;
     return $q.all(allQueryPromise)
     .then(function(allResponse) {
       var result = [];
@@ -160,7 +160,7 @@ export function PrometheusDatasource(instanceSettings, $q, backendSrv, templateS
 
     var interpolated;
     try {
-      interpolated = templateSrv.replace(expr, {}, interpolateQueryExpr);
+      interpolated = templateSrv.replace(expr, {}, this.interpolateQueryExpr);
     } catch (err) {
       return $q.reject(err);
     }

public/app/plugins/datasource/prometheus/query_ctrl.ts

@@ -61,7 +61,7 @@ class PrometheusQueryCtrl extends QueryCtrl {
     var rangeDiff = Math.ceil((range.to.valueOf() - range.from.valueOf()) / 1000);
     var endTime = range.to.utc().format('YYYY-MM-DD HH:mm');
     var expr = {
-      expr: this.templateSrv.replace(this.target.expr, this.panelCtrl.panel.scopedVars),
+      expr: this.templateSrv.replace(this.target.expr, this.panelCtrl.panel.scopedVars, this.datasource.interpolateQueryExpr),
       range_input: rangeDiff + 's',
       end_input: endTime,
       step_input: '',