Missing tethering stats isn't an error.

When a device first boots, there won't be any tethering stats, which
isn't an error.  Continue checking for partial results.

Bug: 5868832
Change-Id: Ic432f5f159320da9886d85c2525fa2cde8c67750
diff --git a/BandwidthController.cpp b/BandwidthController.cpp
index e31a515..664211d 100644
--- a/BandwidthController.cpp
+++ b/BandwidthController.cpp
@@ -1098,7 +1098,6 @@
     TetherStats stats;
     char *buffPtr;
     int64_t packets, bytes;
-    int statsFound = 0;
 
     bool filterPair = filter.intIface[0] && filter.extIface[0];
 
@@ -1174,11 +1173,10 @@
                 stats = filter;
             }
             free(msg);
-            statsFound++;
         }
     }
-    /* We found some stats, and the last one isn't a partial stats. */
-    if (statsFound && (stats.rxBytes == -1 || stats.txBytes == -1)) {
+    /* Successful if the last stats entry wasn't partial. */
+    if ((stats.rxBytes == -1) == (stats.txBytes == -1)) {
         cli->sendMsg(ResponseCode::CommandOkay, "Tethering stats list completed", false);
         return 0;
     }