Revert "Revert "clear the searchbox after quick-search""

This reverts commit 844ea390c8.

src/components/structures/SearchBox.js

@@ -48,18 +48,14 @@ module.exports = React.createClass({
     },
 
     onAction: function(payload) {
-        // Disabling this as I find it really really annoying, and was used to the
-        // previous behaviour - see https://github.com/vector-im/riot-web/issues/3348
-/*        
         switch (payload.action) {
             // Clear up the text field when a room is selected.
             case 'view_room':
-                if (this.refs.search) {
+                if (payload.clear_search && this.refs.search) {
                     this._clearSearch();
                 }
                 break;
         }
-*/        
     },
 
     onChange: function() {