Added unit test of iptables

[yashsingh74]

This PR includes the unit test of iptables.

Output:

> go test iptables_test.go -v
=== RUN   TestParseIPTablesData
=== RUN   TestParseIPTablesData/basic_test
=== RUN   TestParseIPTablesData/not_enough_tables
=== RUN   TestParseIPTablesData/trailing_junk
=== RUN   TestParseIPTablesData/bad_start_line
=== RUN   TestParseIPTablesData/no_nat
=== RUN   TestParseIPTablesData/no_filter
--- PASS: TestParseIPTablesData (0.00s)
    --- PASS: TestParseIPTablesData/basic_test (0.00s)
    --- PASS: TestParseIPTablesData/not_enough_tables (0.00s)
    --- PASS: TestParseIPTablesData/trailing_junk (0.00s)
    --- PASS: TestParseIPTablesData/bad_start_line (0.00s)
    --- PASS: TestParseIPTablesData/no_nat (0.00s)
    --- PASS: TestParseIPTablesData/no_filter (0.00s)
PASS
ok  	command-line-arguments	0.389s

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: yashsingh74 / name: Yash Singh (0ba2de3)

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[jayunit100]

thank you ! rebase then we can merge

[jayunit100]

Hi @yashsingh74 can you file an issue for this ? Just to clarify what parts of the existing codebase were adding test coverage for

[jayunit100]

/lgtm
/approve

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[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: jayunit100, yashsingh74

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