Need enough time (1 sec) to read amounts of packet from /proc/stat_uid/[uid]/tcp_snd.

Change-Id: I93fdd1bc383e8b944a76e211166e2c5fdb9707cd
diff --git a/tests/tests/net/src/android/net/cts/TrafficStatsTest.java b/tests/tests/net/src/android/net/cts/TrafficStatsTest.java
index ee37244..9d23a87 100644
--- a/tests/tests/net/src/android/net/cts/TrafficStatsTest.java
+++ b/tests/tests/net/src/android/net/cts/TrafficStatsTest.java
@@ -170,6 +170,12 @@
             server.close();
         }
 
+        // It's too fast to call getUidTxBytes function.
+        try {
+            Thread.sleep(1000);
+        } catch (InterruptedException e) {
+        }
+
         long mobileTxPacketsAfter = TrafficStats.getTotalTxPackets();
         long mobileRxPacketsAfter = TrafficStats.getTotalRxPackets();
         long mobileTxBytesAfter = TrafficStats.getTotalTxBytes();