[lag_member] add missing imports required to test (#16021)

During movement test to Python 3 (#14944), were deleted necessary imports of fixtures with "autouse=True":
copy_ptftests_directory
copy_arp_responder_py

copy_arp_responder_py:
The fixture copied required configuration files. The arp responder configurations used in the test by method setup_arp_responder

Signed-off-by: AntonHryshchuk <[email protected]>

Author: AntonHryshchuk

tests/pc/test_lag_member.py

@@ -10,7 +10,7 @@
 from tests.common.helpers.assertions import pytest_assert, pytest_require
 from tests.ptf_runner import ptf_runner
 from tests.common.utilities import wait_until
-from tests.common.fixtures.ptfhost_utils import copy_acstests_directory # noqa F401
+from tests.common.fixtures.ptfhost_utils import copy_acstests_directory, copy_ptftests_directory, copy_arp_responder_py # noqa F401
 from tests.common.config_reload import config_reload
 
 logger = logging.getLogger(__name__)