[3.7] bpo-35352: test_asyncio uses the certificate set from the test directory (GH...

[3.7] bpo-35352: test_asyncio uses the certificate set from the test directory (GH-10826) (GH-10834)

* bpo-35352: test_asyncio uses the certificate set from the test directory (GH-10826)

Modify asyncio tests to utilize the certificates from the test directory
instead of its own set, as they are the same and with each update they had
to be updated as well.

(cherry picked from commit b062ba77b617b0f89b7ea25d14cc77c991462ad4)

* bpo-35352: Cleanup test_asyncio/utils.py (GH-10831)

'here' variable is no longer needed.

(cherry picked from commit 7212148c95947b0fdfcb0c8e37d4357287bdb4bd)