Update nic_simulator.py to avoid errors when retrieving packet_filter variable

[svelamal]

Description of PR

Class variable slots does not include packet_filter and drop instances which are accessed later. This causes the nic-simulator to not run successfully and add-topo on Active-Active topology does not work
Summary:
Fixes # (issue)

Type of change

• Bug fix
• Testbed and Framework(new/improvement)
• Test case(new/improvement)

Back port request

• 201911
• 202012
• [x ] 202205

Approach

What is the motivation for this PR?

How did you do it?

How did you verify/test it?

Any platform specific information?

Supported testbed topology if it's a new test case?

Documentation

[mssonicbld]

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