Includes general improvements and bug fixes.

• Include the user data directory in the benchmark name Include the user data directory in the benchmark name #311
• Use existing Elasticsearch indices to speed up transfer during a restore Use existing Elasticsearch indices to speed up transfer during a restore #310
• Improve detection of failures in cluster backup rsync threads Improve detection of failures in cluster backup rsync threads #301
• Improve redis backup robustness Retry loop for redis-cli BGSAVE #306
• Use default niceness for restores Use default niceness for restores #308
• Add additional case to SSH port detection logic Change the condition in *ghe-host-check* when access through port 22 fails  #304
• Suppress additional dd output noise Suppress dd output noise #289
• Track completeness of Elasticsearch JSON dumps Track completeness of Elasticsearch JSON dumps #298

/cc @github/backup-utils