Fix IndexCollection propagation into plugin guice injectors

This fixes a regression caused by: I3c4616d08e. As the consequence
index collection instances were not correctly propagated into plugin's
Guice injectors. A test is added in singleusergroup plugin to avoid such
breakages in future.

Bug: Issue 8398
Change-Id: I87e29a798a83b03f9daa2cfe4708d89becae201e

gerrit-server/src/main/java/com/google/gerrit/server/plugins/PluginGuiceEnvironment.java

@@ -34,6 +34,7 @@ import com.google.gerrit.extensions.registration.RegistrationHandle;
 import com.google.gerrit.extensions.registration.ReloadableRegistrationHandle;
 import com.google.gerrit.extensions.systemstatus.ServerInformation;
 import com.google.gerrit.extensions.webui.WebUiPlugin;
+import com.google.gerrit.index.IndexCollection;
 import com.google.gerrit.metrics.MetricMaker;
 import com.google.gerrit.server.util.PluginRequestContext;
 import com.google.gerrit.server.util.RequestContext;
@@ -568,7 +569,7 @@ public class PluginGuiceEnvironment {
     Class<?> type = key.getTypeLiteral().getRawType();
     if (LifecycleListener.class.isAssignableFrom(type)
         // This is needed for secondary index to work from plugin listeners
-        && !is("com.google.gerrit.server.index.IndexCollection", type)) {
+        && !IndexCollection.class.isAssignableFrom(type)) {
       return false;
     }
     if (StartPluginListener.class.isAssignableFrom(type)) {