Enable linters for test packages

[saima-s]

Is your feature request related to a problem? Please describe.
As of now linters are disabled from test packages in .golangci.yaml file:

issues:
  exclude-rules:
    - path: '_test.go'
      linters:
        - errcheck                      # Errors may be ignored in tests.
        - unparam                       # Tests might have unused function parameters.
        - lll
        - dupl
        - misspell
        - nestif
        - gci

Describe the solution you'd like
After enabling this linter, fix all kind of linter issues coming up in test packages.

[anishbista60]

/assign
please assign to me. I'll work .

[julio-lopez]

This should not have been closed in #3052

[hairyhum]

@anishbista60 can you please provide more context to the PRs mentioning that linters are actually being added and not removed?

[anishbista60]

@hairyhum ok ok . Sorry , description was wrong.

[anishbista60]

@julio-lopez I think it should not be closed.

[julio-lopez]

@julio-lopez I think it should not be closed.

It was automatically closed because this PR's description said "fixes: #2962"

@anishbista60 Please make sure that the PRs and the commits say "Ref #2962" and not "fixes".