Rename the dir for SystemUpdaterSample.

Also replace the occurrence in README.md and PREUPLOAD.cfg.

Test: mmma -j bootable/recovery
Change-Id: I04c0ef00dd64f49e008ad2a4a2c1e8eaed76bf8d
diff --git a/Android.mk b/Android.mk
index e54db2d..eef4a02 100644
--- a/Android.mk
+++ b/Android.mk
@@ -199,7 +199,7 @@
 include \
     $(LOCAL_PATH)/boot_control/Android.mk \
     $(LOCAL_PATH)/minui/Android.mk \
-    $(LOCAL_PATH)/sample_updater/Android.mk \
     $(LOCAL_PATH)/tests/Android.mk \
     $(LOCAL_PATH)/tools/Android.mk \
     $(LOCAL_PATH)/updater/Android.mk \
+    $(LOCAL_PATH)/updater_sample/Android.mk \