Tune up TIMEOUTs of IPSec CTS for low end devices

Ikev2VpnTest#testStartStopVpnProfileV4 and testStartStopVpnProfileV6
contains the IKE sequences and requires the phone to send and receive
the required packet in 1000ms.
On some low end devices, the response time may exceeds this TIMEOUT
sometimes.
So we need to use larger timeouts.

Bug: 171176723
Change-Id: I005b83ffecd8ade5063000690bfd4136d82f1a07
diff --git a/tests/cts/net/src/android/net/cts/TunUtils.java b/tests/cts/net/src/android/net/cts/TunUtils.java
index adaba9d..7887385 100644
--- a/tests/cts/net/src/android/net/cts/TunUtils.java
+++ b/tests/cts/net/src/android/net/cts/TunUtils.java
@@ -47,7 +47,7 @@
     protected static final int IP6_PROTO_OFFSET = 6;
 
     private static final int DATA_BUFFER_LEN = 4096;
-    private static final int TIMEOUT = 1000;
+    private static final int TIMEOUT = 2000;
 
     private final List<byte[]> mPackets = new ArrayList<>();
     private final ParcelFileDescriptor mTunFd;