Includes general improvements & bug fixes

• Make it clear the settings need to be applied after restoring to an unconfigured instance Make it clear the settings need to be applied after restoring to an unconfigured instance  #381
• Remove check for git from ghe-ssh Remove check for git from ghe-ssh #393
• Use remote's mktemp to create temp dir on remote host Use remote's mktemp to create temp dir on remote host #395
• Enabling concurrent ghe-backup tasks from separate backup hosts github/ghes#7628

/cc @github/backup-utils