fix test_aiohttp_loop (Azure#20811)

* fix test_aiohttp_loop

* fix collections import issue

Author: xiangyan99

sdk/core/azure-core/tests/test_basic_transport.py

@@ -1171,6 +1171,6 @@ def test_conflict_timeout(caplog, port, http_request):
 def test_aiohttp_loop():
     import asyncio
     from azure.core.pipeline.transport import AioHttpTransport
-    loop = asyncio._get_running_loop()
+    loop = asyncio.get_event_loop()
     with pytest.raises(ValueError):
         transport = AioHttpTransport(loop=loop)

sdk/core/azure-core/tests/test_rest_http_request.py

@@ -10,7 +10,10 @@
 import io
 import pytest
 import sys
-import collections
+try:
+    import collections.abc as collections
+except ImportError:
+    import collections  # type: ignore
 
 from azure.core.configuration import Configuration
 from azure.core.rest import HttpRequest