Set Ethernet default mode as CLIENT

Bug: 130840861
Test: build, boot
      atest EthernetTrackerTest
      manual test (using Ethernet)

Change-Id: I935ea2e5f214aced67fb60f4aec2744077177545
diff --git a/java/com/android/server/ethernet/EthernetTracker.java b/java/com/android/server/ethernet/EthernetTracker.java
index 24616b7..58803d1 100644
--- a/java/com/android/server/ethernet/EthernetTracker.java
+++ b/java/com/android/server/ethernet/EthernetTracker.java
@@ -90,7 +90,7 @@
 
     // Used only on the handler thread
     private String mDefaultInterface;
-    private int mDefaultInterfaceMode;
+    private int mDefaultInterfaceMode = INTERFACE_MODE_CLIENT;
     // Tracks whether clients were notified that the tethered interface is available
     private boolean mTetheredInterfaceWasAvailable = false;
     private volatile IpConfiguration mIpConfigForDefaultInterface;