[HAMMER] [V2V] Refactor ConversionHost to use AuthenticationMixin

[djberg96]

This is essentially a clone of #18309. The primary difference is that this PR does not modify the AuthenticationMixin module. Doing so caused failures in at least one provider.

BZ: https://bugzilla.redhat.com/show_bug.cgi?id=1702051

Replaces #18634 which I got goofed up on a botched rebase.

[Fryguy]

@agrare Can you take a look at this?

[djberg96]

@agrare Hang on, need to fix something, accidentally mixed in code from a different PR.
Ok, updated.

[miq-bot]

Checked commits https://github.com/djberg96/manageiq/compare/11ae1363e71c297d42990fdecb6c1a14a95f7313~...88b1d8655eac610dec0f849be88dda04c83f1273 with ruby 2.3.3, rubocop 0.52.1, haml-lint 0.20.0, and yamllint 1.10.0
4 files checked, 3 offenses detected

app/models/conversion_host.rb

• ⚠️ - Line 76, Col 3 - Lint/RescueException - Avoid rescuing the Exception class. Perhaps you meant to rescue StandardError?
• ❗ - Line 215, Col 7 - Layout/MultilineOperationIndentation - Align the operands of an expression in an assignment spanning multiple lines.
• ❗ - Line 216, Col 7 - Layout/MultilineOperationIndentation - Align the operands of an expression in an assignment spanning multiple lines.

[agrare]

@djberg96 so without the change to the AuthenticationMixin what else had to change on this backport? This looks identical as far as I can see with a quick once over

[djberg96]

@agrare The difference was the behavior change in available_authentications and authentication_key_pairs.

[djberg96]

@agrare Oh, misread that last comment. Didn't think anything else needed to change since it's just openstack and rhev for now.