InitCommand: Don't leave Repository open after Git is closed

InitCommand: Don't leave Repository open after Git is closed

The InitCommand returns a Git that is instantiated with the newly
created Repository, but the Repository is not closed with the Git
resulting in resource leaks.

Create the Git with `closeRepo` set to true, such that the Repository
is also closed when the Git is closed.

Adjust the tests to use try-with-resource on the Git instance.

Change-Id: Ib26e7428c7d8840956d1edb09e53b93e23e6fe5a
Signed-off-by: David Pursehouse <david.pursehouse@gmail.com>