Test Managed Transport

[pjbgf]

The Git related tests must be refactored to ensure the Managed Transport is being used.
Given that a lot of the testing logic is based on git2go, by enabling the Manage Transport of the controller we are also changing the behaviour of the tests themselves.

Extra points to consider:

• libgit2 checkout func now have the side effect of removing the Transport Options even if they were added by the caller. We probably want to change this.
• Run both managed and unmanaged tests whilst we support the latter.

[pjbgf]

Managed transport has been deprecated since v0.24.0 and therefore this is no longer required.