[Tests]Increase timeout for shell command to ping.

Bug: 93271682
Test: Local
Change-Id: I272dd3f22e22355ec74d7f2f4f2edc461c6c0080
diff --git a/acts/tests/google/wifi/WifiStressTest.py b/acts/tests/google/wifi/WifiStressTest.py
index 063f557..0eab3ad 100755
--- a/acts/tests/google/wifi/WifiStressTest.py
+++ b/acts/tests/google/wifi/WifiStressTest.py
@@ -129,7 +129,8 @@
 
         """
         self.log.info("Running ping for %d seconds" % sec)
-        result = self.dut.adb.shell("ping -w %d %s" %(sec, PING_ADDR))
+        result = self.dut.adb.shell("ping -w %d %s" %(sec, PING_ADDR),
+            timeout=sec+1)
         self.log.debug("Ping Result = %s" % result)
         if "100% packet loss" in result:
             raise signals.TestFailure("100% packet loss during ping")