Skip testRouterSolicitations on T- devices.

This does not lways pass on some devices before U. Now that the
test is being added to MCTS, and needs to be backwards
compatible, skip this test on T- devices.

Test: atest CtsHostsideNetworkTests
Change-Id: I2368f118d2539d70a97c937485f5179c47ba28d7
diff --git a/tests/cts/hostside/src/com/android/cts/net/ProcNetTest.java b/tests/cts/hostside/src/com/android/cts/net/ProcNetTest.java
index fa68e3e..ae572e6 100644
--- a/tests/cts/hostside/src/com/android/cts/net/ProcNetTest.java
+++ b/tests/cts/hostside/src/com/android/cts/net/ProcNetTest.java
@@ -166,6 +166,8 @@
      */
     @Test
     public void testRouterSolicitations() throws Exception {
+        assumeTrue(new DeviceSdkLevel(mDevice).isDeviceAtLeastU());
+
         for (String interfaceDir : mSysctlDirs) {
             String path = IPV6_SYSCTL_DIR + "/" + interfaceDir + "/" + "router_solicitations";
             int value = readIntFromPath(path);
@@ -186,8 +188,7 @@
      */
     @Test
     public void testCongestionControl() throws Exception {
-        final DeviceSdkLevel dsl = new DeviceSdkLevel(mDevice);
-        assumeTrue(dsl.isDeviceAtLeastV());
+        assumeTrue(new DeviceSdkLevel(mDevice).isDeviceAtLeastV());
 
         String path = "/proc/sys/net/ipv4/tcp_congestion_control";
         String value = mDevice.executeAdbCommand("shell", "cat", path).trim();