bpo-30106: Fix tearDown() of test_asyncore (#1194)

Call asyncore.close_all() with ignore_all=True in the tearDown()
method of the test_asyncore base test case. It should prevent keeping
alive sockets in asyncore.socket_map if close() fails with an
unexpected error.

Revert also an unwanted change of my previous commit: remove name
parameter of Thread in test_quick_connect().