GUACAMOLE-822: Correct retrieval of client identifier for connection groups.

Commit f92bf9c moved the getClientIdentifier() function to the
GroupListItem class, thus making the function available as
item.getClientIdentifier() within the connection or connection group
templates referenced by an instance of the guacGroupList directive.

This change correctly updated all but the connection group template for
the home screen, which was incorrectly updated to reference the
function as if it were directly on the scope. As such a function
doesn't exist, AngularJS didn't substitute any value, resulting in a
non-functional link.

guacamole/src/main/webapp/app/home/templates/connectionGroup.html

@@ -1,4 +1,4 @@
 <span class="home-connection-group name">
-    <a ng-show="item.balancing" ng-href="#/client/{{ getClientIdentifier() }}">{{item.name}}</a>
+    <a ng-show="item.balancing" ng-href="#/client/{{ item.getClientIdentifier() }}">{{item.name}}</a>
     <span ng-show="!item.balancing">{{item.name}}</span>
 </span>