Use the new ovirt-hosted-engine-ha Backend API for lockspace init

ovirt-hosted-engine-ha unified the API for creating and accessing
the metadata and lockspace files.

This patch removes the code duplication between setup and ha using
the API.

Change-Id: I4ca5539aa45742eb99577a5c91200fdadf555a11
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=1067162
Signed-off-by: Martin Sivak <msivak@redhat.com>