Address comment about redis-cli vs sonic-db-cli.

This failed the test:

admin@vlab-01:~$ sonic-db-cli CONFIG_DB KEYS "TELEMETRY|*"
TELEMETRY|gnmi
TELEMETRY|certs

After configuration. Unknown reason but indeed reflect a problem about
the previous process.

tests/l2/test_l2_configure.py

@@ -72,7 +72,7 @@ def test_l2_config_and_upgrade(request, duthosts, rand_one_dut_hostname, localho
     # Step 4: Verifies no config fro minigraph is written into ConfigDB.
     try:
         for table in ["TELEMETRY", "RESTAPI", "DEVICE_METADATA"]:
-            count = int(duthost.shell('redis-cli --scan --pattern "{}*" | wc -l'.format(table))['stdout'])
+            count = int(duthost.shell('sonic-db-cli CONFIG_DB KEYS "{}|* | wc -l'.format(table))['stdout'])
             pytest_assert(count == 0, "{} table is not empty!".format(table))
     except Exception:
         raise