Update port2alias (sonic-net#3217)

Basically port2alias Cli became broken on multi-asic platforms after introduction of sonic-net/sonic-buildimage#10960 which removed the initialization of global DB config from portconfig.py (library side) and expects application to do it, but here application side (port2alias) was not updated accordingly.

How I did it
Add load_db_config call to port2alias for initialization

scripts/port2alias

@@ -7,6 +7,7 @@ from io import StringIO
 from portconfig import get_port_config
 from sonic_py_common import device_info
 from sonic_py_common import multi_asic
+from utilities_common.general import load_db_config
 
 # mock the redis for unit test purposes #
 try:
@@ -50,6 +51,7 @@ def translate_line(line, ports):
 def main():
     (platform, hwsku) = device_info.get_platform_and_hwsku()
     ports = {}
+    load_db_config()
     for ns in multi_asic.get_namespace_list():
         (ports_ns, _, _) = get_port_config(hwsku=hwsku, platform=platform, asic_name=ns)
         ports.update(ports_ns)