[PFC] pfc config commands lead to traceback due to KeyError

[gpunathilell]

Description

After addition of the following PR in sonic-utilities sonic-net/sonic-utilities#3521 pfc config commands fail with the following error KeyError: 'UTILITIES_UNIT_TESTING' due to the UTILITIES_UNIT_TESTING environment variable not being configured. This variable is being accessed in the dump_config_to_json function as shown here

Steps to reproduce the issue:

1. Deploy latest master image with updated sonic-utilities
2. Execute pfc config command (Ex: pfc config assymmetric on Ethernet64)

Describe the results you received:

root@sonic:~# pfc config asymmetric on Ethernet64
Traceback (most recent call last):
  File "/usr/local/bin/pfc", line 8, in <module>
    sys.exit(cli())
             ^^^^^
  File "/usr/local/lib/python3.11/dist-packages/click/core.py", line 764, in __call__
    return self.main(*args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/dist-packages/click/core.py", line 717, in main
    rv = self.invoke(ctx)
         ^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/dist-packages/click/core.py", line 1137, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
                           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/dist-packages/click/core.py", line 1137, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
                           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/dist-packages/click/core.py", line 956, in invoke
    return ctx.invoke(self.callback, **ctx.params)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/dist-packages/click/core.py", line 555, in invoke
    return callback(*args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/dist-packages/pfc/main.py", line 167, in configAsym
    Pfc(namespace).configPfcAsym(interface, status)
  File "/usr/local/lib/python3.11/dist-packages/utilities_common/multi_asic.py", line 156, in wrapped_run_on_all_asics
    func(self,  *args, **kwargs)
  File "/usr/local/lib/python3.11/dist-packages/pfc/main.py", line 47, in configPfcAsym
    self.dump_config_to_json(PORT_TABLE_NAME, self.multi_asic.current_namespace)
  File "/usr/local/lib/python3.11/dist-packages/pfc/main.py", line 31, in dump_config_to_json
    if os.environ["UTILITIES_UNIT_TESTING"] != "2":
       ~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "<frozen os>", line 679, in __getitem__
KeyError: 'UTILITIES_UNIT_TESTING'

Describe the results you expected:

No traceback should appear

Additional information you deem important (e.g. issue happens only occasionally):

Issue can be solved by handling the call in a try except block as shown here and here or use the get method

[dgsudharsan]

@arista-hpandya Can you please prioritize fixing this? @prsunny @qiluo-msft for visibility

[arista-hpandya]

Fix included in the linked PR. Thank you for catching this issue!