Make testProcessMemoryHighWaterMark more reliable

Currently the data may be pulled before the process is fully
initialized. So we insert an extra sleep indentical to what
another test, testProcessMemoryState, does.

Test: the test pass on emulator with native-bridge support
Bug: 145629448
Change-Id: Iddb8518a2430468bc89eb7776223b7003eaa9848
diff --git a/hostsidetests/statsd/src/android/cts/statsd/atom/UidAtomTests.java b/hostsidetests/statsd/src/android/cts/statsd/atom/UidAtomTests.java
index c279c49..446d90f 100644
--- a/hostsidetests/statsd/src/android/cts/statsd/atom/UidAtomTests.java
+++ b/hostsidetests/statsd/src/android/cts/statsd/atom/UidAtomTests.java
@@ -1144,6 +1144,8 @@
         // Start test app and trigger a pull while its running.
         try (AutoCloseable a = withActivity("StatsdCtsForegroundActivity", "action",
                 "action.show_notification")) {
+            Thread.sleep(WAIT_TIME_SHORT);
+            // Trigger a pull and wait for new pull before killing the process.
             setAppBreadcrumbPredicate();
             Thread.sleep(WAIT_TIME_LONG);
         }