Stable/havana

Commit to address 2 issues:

1. For some disks which had a previous file system (e.g., ZFS), it does not work properly to format with XFS directly.  As a workaround, we format to EXT4 first and then to XFS which seems to work fine.
2. For some disks having a previous partition table, the checks for partitioning were passing even though the partitions were not the desired GPT partitions.