wifi: Fix unit test error

The default timeout value is changed to -1 after T.
Since the migration module is not a part of mainline.
So fix unit test it directly for T unit test error.

For old device, it should still use old unit test version with old value and get pass
because the getShutdownTimeoutMillis() returns old value on old build.

Bug: 213289672
Test: atest -c android.net.wifi.SoftApConfToXmlMigrationUtilTest#testConversion
Change-Id: Ia14b019101b8e78fc3f7374c907453508dfea420

wifi/tests/src/android/net/wifi/SoftApConfToXmlMigrationUtilTest.java

@@ -56,7 +56,7 @@ public class SoftApConfToXmlMigrationUtilTest {
                     + "<int name=\"MaxNumberOfClients\" value=\"0\" />\n"
                     + "<boolean name=\"ClientControlByUser\" value=\"false\" />\n"
                     + "<boolean name=\"AutoShutdownEnabled\" value=\"true\" />\n"
-                    + "<long name=\"ShutdownTimeoutMillis\" value=\"0\" />\n"
+                    + "<long name=\"ShutdownTimeoutMillis\" value=\"-1\" />\n"
                     + "<BlockedClientList />\n"
                     + "<AllowedClientList />\n"
                     + "</SoftAp>\n"