Remove Exception in getRegisteredExperimentIds

This check was not useful since service can only be null if system
server is not running or the app does not have permissions to access
statsd. This check is not done anywhere else, so removing it for
consistency.

Bug: 150645647
Test: atest StatsdHostTestCases
Change-Id: I6465697f0157c5a9583025979c55cb2e3dc1ef84
diff --git a/apex/framework/java/android/app/StatsManager.java b/apex/framework/java/android/app/StatsManager.java
index f021dcf..ed57151 100644
--- a/apex/framework/java/android/app/StatsManager.java
+++ b/apex/framework/java/android/app/StatsManager.java
@@ -467,10 +467,6 @@
         synchronized (sLock) {
             try {
                 IStatsManagerService service = getIStatsManagerServiceLocked();
-                if (service == null) {
-                    throw new StatsUnavailableException("Failed to find statsmanager when "
-                                                              + "getting experiment IDs");
-                }
                 return service.getRegisteredExperimentIds();
             } catch (RemoteException e) {
                 if (DEBUG) {