Fix edit annotation rendering speed

The editTemplateVariableNames action would fire way too many times.
This cause poor rendering speeds with annotations.

ui/src/shared/middleware/queryStringConfig.js

@@ -4,19 +4,27 @@ import queryString from 'query-string'
 import {enablePresentationMode} from 'src/shared/actions/app'
 import {templateVariablesSelectedByName} from 'src/dashboards/actions'
 
-export const queryStringConfig = () => next => action => {
-  next(action)
-  const qs = queryString.parse(window.location.search)
+export const queryStringConfig = () => {
+  let prevPath
+  return next => action => {
+    next(action)
+    const qs = queryString.parse(window.location.search)
 
-  // Presentation Mode
-  if (qs.present === 'true') {
-    next(enablePresentationMode())
-  }
+    // Presentation Mode
+    if (qs.present === 'true') {
+      next(enablePresentationMode())
+    }
 
-  // Select Template Variable By Name
-  const dashboardRegex = /\/sources\/(\d+?)\/dashboards\/(\d+?)/
-  if (dashboardRegex.test(window.location.pathname)) {
-    const dashboardID = window.location.pathname.match(dashboardRegex)[2]
-    next(templateVariablesSelectedByName(+dashboardID, qs))
+    // Select Template Variable By Name
+    const dashboardRegex = /\/sources\/(\d+?)\/dashboards\/(\d+?)/
+    if (dashboardRegex.test(window.location.pathname)) {
+      const currentPath = window.location.pathname
+      const dashboardID = currentPath.match(dashboardRegex)[2]
+      if (currentPath !== prevPath) {
+        next(templateVariablesSelectedByName(+dashboardID, qs))
+      }
+
+      prevPath = currentPath
+    }
   }
 }