Close standalone server after using it for end-to-end tests
Close standalone server after using it for end-to-end tests

This patch closes the standalone server after being used at the tests in
test_endtoend.

Change-Id: Iac45d2c80e48e76ad735f7697efa8b6c5f4595d4

GoogleChromeLabs/pywebsocket3,GoogleChromeLabs/pywebsocket3,GoogleChromeLabs/pywebsocket3