Ignore testFactoryReset in instant app mode

testFactoryReset() will need to check wifi enabled state from
WifiManager. However, test can not get WifiManager in instant
app mode, so ignore the test in instant app mode.

Bug: 190800362
Test: atest android.net.cts.ConnectivityManagerTest\
      #testFactoryReset --instant
Change-Id: Icd4a1b2316608ea03a4f7afb32e39400af71950c

tests/cts/net/src/android/net/cts/ConnectivityManagerTest.java

@@ -2010,6 +2010,7 @@ public class ConnectivityManagerTest {
         assertThrows(SecurityException.class, () -> mCm.factoryReset());
     }
 
+    @AppModeFull(reason = "Cannot get WifiManager in instant app mode")
     @Test
     public void testFactoryReset() throws Exception {
         assumeTrue(TestUtils.shouldTestSApis());