Tethering: Add an exported flag in manifest

With b/150232615, we will need an explicit value set for the exported
flag when intent filters are present, as the default behavior is
changing for S+. This change adds the value reflecting the previous
default to the manifest.

Bug: 150232615
Test: TH
Change-Id: I25b55378df393cd4fb8932b7ae64f97eb9f1aa8e
Merged-In: I25b55378df393cd4fb8932b7ae64f97eb9f1aa8e
(cherry picked from commit 9226d6c835cd57d10a7562f18143dbaae8601b43)

Tethering/AndroidManifest.xml

@@ -44,7 +44,8 @@
         android:extractNativeLibs="false"
         android:persistent="true">
         <service android:name="com.android.server.connectivity.tethering.TetheringService"
-                 android:permission="android.permission.MAINLINE_NETWORK_STACK">
+                 android:permission="android.permission.MAINLINE_NETWORK_STACK"
+                 android:exported="true">
             <intent-filter>
                 <action android:name="android.net.ITetheringConnector"/>
             </intent-filter>

Tethering/AndroidManifest_InProcess.xml

@@ -24,7 +24,8 @@
     <application>
         <service android:name="com.android.server.connectivity.tethering.TetheringService"
                  android:process="system"
-                 android:permission="android.permission.MAINLINE_NETWORK_STACK">
+                 android:permission="android.permission.MAINLINE_NETWORK_STACK"
+                 android:exported="true">
             <intent-filter>
                 <action android:name="android.net.ITetheringConnector.InProcess"/>
             </intent-filter>