multiSimAllowed should be consistent with max active modem property.

Bug: 153023231
Test: manual - using test app
Change-Id: I2d38dd9a0a860ee451fe51372a62c2910b88c88f

telephony/java/android/telephony/TelephonyManager.java

@@ -12337,6 +12337,9 @@ public class TelephonyManager {
     @RequiresPermission(android.Manifest.permission.READ_PHONE_STATE)
     @IsMultiSimSupportedResult
     public int isMultiSimSupported() {
+        if (getSupportedModemCount() < 2) {
+            return TelephonyManager.MULTISIM_NOT_SUPPORTED_BY_HARDWARE;
+        }
         try {
             ITelephony service = getITelephony();
             if (service != null) {