Refactor cli/core to fix linter issues

[saji-pivotal]

Bug description
The following linters are failing in the cli/core module. They have been skipped for now, but the code needs to be refactored and tested in order to fully fix the linters

pkg/cli/catalog_test.go
pkg/cluster/client.go
pkg/command/config.go
pkg/command/doc.go
pkg/command/plugin_manager.go
pkg/command/root.go
pkg/command/update.go
pkg/config/bom.go
pkg/pluginmanager/manager.go

Affected product area (please put an X in all that apply)

• ( ) APIs
• ( ) Addons
• (X) CLI
• ( ) Docs
• ( ) IAM
• ( ) Installation
• ( ) Plugin
• ( ) Security
• (X) Test and Release
• () User Experience
• (X) Developer Experience

Expected behavior

Steps to reproduce the bug

Version (include the SHA if the version is not obvious)

Environment where the bug was observed (cloud, OS, etc)

Relevant Debug Output (Logs, manifests, etc)

[vuil]

@saji-pivotal can this be closed?