Make v0.9 ES backup strategy work against GHE v2.0 appliances

The elasticsearch directory is now owned and readable by the
elasticsearch user only.
Move back to single es backup script

We're going to hold off on the ES snapshot API approach until a
future release.
Use rsync instead tar for transferring v11.10.x ES backups to appliance

We needed to use tar for transferring to v11.10.x instances because
we didn't have sudo for controlling permissions on the resulting
files. We can just use rsync directly under v2.x.
Transfer ES backups to elasticsearch-restore directory

The ghe-config-apply command on the VM detects this directory and
moves into the active location.
Fix up backup/restore tests for ES changes
Merge pull request #12 from github/rollback-es-snapshot-api

Rollback to ES disable flush backup method for v2.x appliances
Merge backup-utils/master changes

Conflicts:
	libexec/ghe-restore-es-rsync
Better requirements section headers in TOC
Misc README cleanup
Merge backup-utils-internal/master into backup-utils