Fix import error in test_tunnel_qos_remap for py3 env (sonic-net#8806)

What is the motivation for this PR?
Fix the following issue, it only happened in py3 env, not for py2.
The error is introduced by sonic-net#8317
Signed-off-by: Zhaohui Sun <zhaohuisun@microsoft.com>

tests/qos/test_tunnel_qos_remap.py

@@ -24,7 +24,7 @@
 from .tunnel_qos_remap_base import build_testing_packet, check_queue_counter,\
     dut_config, qos_config, load_tunnel_qos_map, run_ptf_test, toggle_mux_to_host,\
     setup_module, update_docker_services, swap_syncd, counter_poll_config                               # noqa F401
-from tunnel_qos_remap_base import leaf_fanout_peer_info, start_pfc_storm, \
+from .tunnel_qos_remap_base import leaf_fanout_peer_info, start_pfc_storm, \
     stop_pfc_storm, get_queue_counter, disable_packet_aging                                             # noqa F401
 from ptf import testutils
 from ptf.testutils import simple_tcp_packet