Standardize location of AddCommand(...) call

[spew]

All AddCommand(...) calls are now made from the sub-command which adds itself to its root / parent command.

What this PR does / why we need it:
This PR standardizes the location of the AddCommand call to reduce confusion and make it easier to developers to understand the codebase. The choice was made to add call AddCommand in the sub command's init() method as that matches the examples given on the cobra github README.md.

Release note:

NONE

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[spew]

/cc @karan @wangzhen127 @jessicaochen

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[spew]

/assign @karan

[karan]

/lgtm