Added close and rename to MockFile

Change-Id: Ie4a53ed80606d5f697a5d8d8ffd9c44fd7c87769
Reviewed-on: https://gerrit.spotify.net/gerrit/49890
TC-Compile-And-Test: Team City <teamcity@spotify.com>
Reviewed-by: Elias Freider <freider@spotify.com>