PYTHON-4068 Fix AWS ECS Task (#1444)

.evergreen/config.yml

@@ -655,7 +655,14 @@ functions:
              exit 0
           fi
           ${PREPARE_SHELL}
-          .evergreen/run-mongodb-aws-test.sh session-creds
+          set -ex
+          cd ${DRIVERS_TOOLS}/.evergreen/auth_aws
+          . ./activate-authawsvenv.sh
+          . aws_setup.sh ecs
+          export MONGODB_BINARIES="${MONGODB_BINARIES}";
+          export PROJECT_DIRECTORY="${PROJECT_DIRECTORY}";
+          python aws_tester.py ecs
+          cd -
 
   "cleanup":
     - command: shell.exec