Rename getStartedPrefixIndex to getRandomPrefixIndex

Test: builds
Change-Id: I38bba24dd0a1053e3795495cfdc14c9960056ffc
diff --git a/Tethering/src/com/android/networkstack/tethering/PrivateAddressCoordinator.java b/Tethering/src/com/android/networkstack/tethering/PrivateAddressCoordinator.java
index 014e821..ef1adf9 100644
--- a/Tethering/src/com/android/networkstack/tethering/PrivateAddressCoordinator.java
+++ b/Tethering/src/com/android/networkstack/tethering/PrivateAddressCoordinator.java
@@ -194,7 +194,7 @@
             return cachedAddress;
         }
 
-        final int prefixIndex = getStartedPrefixIndex();
+        final int prefixIndex = getRandomPrefixIndex();
         for (int i = 0; i < mTetheringPrefixes.size(); i++) {
             final IpPrefix prefixRange = mTetheringPrefixes.get(
                     (prefixIndex + i) % mTetheringPrefixes.size());
@@ -210,7 +210,7 @@
         return null;
     }
 
-    private int getStartedPrefixIndex() {
+    private int getRandomPrefixIndex() {
         if (!mIsRandomPrefixBaseEnabled) return 0;
 
         final int random = getRandomInt() & 0xffffff;