BUG: metal 2fa enable and metal 2fa disable don't work

[ctreatma]

While migrating the metal 2fa subcommand from packngo to equinix-sdk-go, we found that the enable and disable commands do not appear to work (at least, not as documented or implemented). For the 2fa enable and 2fa disable subcommands, the same failure happens in both the packngo and equinix-sdk-go implementations:

HTTP/1.1 424 Failed Dependency
{"errors":["Invalid OTP"]}

Since this is a pre-existing issue and isn't caused or fixed by the SDK migration, I'm advocating to handle it in a separate issue & PR.

Originally posted by @ctreatma in #353 (comment)