Add system prop to work around tether provisioning

Set net.tethering.noprovisioning to something non-empty to avoid the provisioning check.

bug:5445277
Change-Id: I048bffe2c11d80d79e8065f7fbe6cfb6db87da85
diff --git a/src/com/android/settings/TetherSettings.java b/src/com/android/settings/TetherSettings.java
index e27c96e..d6f6ab6 100644
--- a/src/com/android/settings/TetherSettings.java
+++ b/src/com/android/settings/TetherSettings.java
@@ -37,6 +37,7 @@
 import android.net.wifi.WifiManager;
 import android.os.Bundle;
 import android.os.Environment;
+import android.os.SystemProperties;
 import android.preference.CheckBoxPreference;
 import android.preference.Preference;
 import android.preference.PreferenceScreen;
@@ -476,6 +477,9 @@
     }
 
     boolean isProvisioningNeeded() {
+        if (SystemProperties.getBoolean("net.tethering.noprovisioning", false)) {
+            return false;
+        }
         return mProvisionApp.length == 2;
     }