Fix kv -mount flag error when mount and secret path are the same

[ccapurso]

Using the -mount flag with kv subcommands fails with the following error when the mount and secret paths are the same:

❯ vault kv get -mount=secret secret

WARNING! The following warnings were returned from Vault:

  * Non-listing operations on the root of a K/V v2 mount are not supported.

== Secret Path ==
secret/data

The fix results in basically the same change across many files. Given the distributed nature of the logic it could benefit from some refactoring but fixing the issue first and introducing some consolidation of logic at a later date if we determine that's prudent seemed safer.

Fixes #17576
Fixes #16639

[digivava]

Thank you for taking the time to fix this edge case! Much appreciated.