no-op: use stopTetheringInternal when restarting tethering on start

startTethering will sometimes restart tethering if there is an existing
request of the same type but with different contents. This call is
equivalent to stopTetheringInternal, so use that instead for simplicity.

Bug: 216524590
Test: covered by existing tests
Change-Id: I224c10557c2348e2d2f971e1e3ecb11ae346d2cf

Tethering/src/com/android/networkstack/tethering/Tethering.java

@@ -708,8 +708,7 @@ public class Tethering {
             // If tethering is already enabled with a different request,
             // disable before re-enabling.
             if (unfinishedRequest != null && !unfinishedRequest.equalsIgnoreUidPackage(request)) {
-                enableTetheringInternal(false /* disabled */, unfinishedRequest, null);
-                mEntitlementMgr.stopProvisioningIfNeeded(type);
+                stopTetheringInternal(type);
             }
             mPendingTetheringRequests.put(type, request);