av: replace getService with waitForService

- getService is deprecated, following ag/21610323 to remove similar
  pattterns

Test: build
Bug: 284487308
Change-Id: I2a2e90fdcf1e2c1ea025935c3e76eeff6b97fd5f
diff --git a/media/libmedia/mediametadataretriever.cpp b/media/libmedia/mediametadataretriever.cpp
index 2ae76b3..40fd022 100644
--- a/media/libmedia/mediametadataretriever.cpp
+++ b/media/libmedia/mediametadataretriever.cpp
@@ -41,14 +41,10 @@
     if (sService == 0) {
         sp<IServiceManager> sm = defaultServiceManager();
         sp<IBinder> binder;
-        do {
-            binder = sm->getService(String16("media.player"));
-            if (binder != 0) {
-                break;
-            }
-            ALOGW("MediaPlayerService not published, waiting...");
-            usleep(500000); // 0.5 s
-        } while (true);
+        binder = sm->waitForService(String16("media.player"));
+        if (binder == nullptr) {
+            return nullptr;
+        }
         if (sDeathNotifier == NULL) {
             sDeathNotifier = new DeathNotifier();
         }