Closes #14421: use with statement to properly close socket in bandwidth test.

Tools/ccbench/ccbench.py

@@ -435,7 +435,7 @@ def run_bandwidth_client(**kwargs):
 def run_bandwidth_test(func, args, nthreads):
     # Create a listening socket to receive the packets. We use UDP which should
     # be painlessly cross-platform.
-    sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
+    with socket.socket(socket.AF_INET, socket.SOCK_DGRAM) as sock:
         sock.bind(("127.0.0.1", 0))
         addr = sock.getsockname()