Fix CTS case testStartUsingNetworkFeature of ConnectivityManagerTest

Check if type of network is supported on the devices.
The device supporting TYPE_WIFI returns failureCode(-1).
But, not supported device returns wifiOnlyStartFailureCode or
wifiOnlyStopFailureCode.

Change-Id: I070bb19f6740367c476e78b884c2a36d111ff3ee
diff --git a/tests/cts/net/src/android/net/cts/ConnectivityManagerTest.java b/tests/cts/net/src/android/net/cts/ConnectivityManagerTest.java
index cd80be2..4704582 100644
--- a/tests/cts/net/src/android/net/cts/ConnectivityManagerTest.java
+++ b/tests/cts/net/src/android/net/cts/ConnectivityManagerTest.java
@@ -161,9 +161,14 @@
                     invalidateFeature));
         }
 
-        // Should return failure(-1) because MMS is not supported on WIFI.
-        assertEquals(failureCode, mCm.startUsingNetworkFeature(TYPE_WIFI, mmsFeature));
-        assertEquals(failureCode, mCm.stopUsingNetworkFeature(TYPE_WIFI, mmsFeature));
+        ni = mCm.getNetworkInfo(TYPE_WIFI);
+        if (ni != null) {
+            // Should return failure(-1) because MMS is not supported on WIFI.
+            assertEquals(failureCode, mCm.startUsingNetworkFeature(TYPE_WIFI,
+                    mmsFeature));
+            assertEquals(failureCode, mCm.stopUsingNetworkFeature(TYPE_WIFI,
+                    mmsFeature));
+        }
     }
 
     @TestTargetNew(