Start qps_scan x at 0 too

analyze/memcached_qps_scan.py

@@ -73,6 +73,7 @@ def show_plot(threads, include_caladan = False):
     plt.xlabel('QPS')
     plt.ylabel('Latency (99th percentile)')
     plt.yscale('log')
+    plt.xlim(xmin = 0)
 
     plt.legend()
     if os.getenv('SAVE_FIGURE') != 'true':