Improved backup commands (#8597)
Improved backup commands (#8597)

* Improved backup commands

DTR image backup command improvements:

1. Local and NFS mount image backup commands were invalid (incorrectly used -C flag). Replaced them with commands that work.
2. The new commands automatically populate the correct replica ID and add a datestamp to the backup filename.

DTR Metadata backup command improvements:

DTR metadata backups are more difficult than they need to be and generate many support tickets. I updated the DTR command to avoid common user pitfalls:

1. The prior metadata backup command was subject to user error. Improved the command to automatically collect the DTR version and select a replica. 
2. Improved security of the command by automatically collecting UCP CA certificate for verification rather than using --ucp-insecure-tls flag. 
3. Improved the backup filename by adding the backed-up version information and date of backup. Knowledge of the version information is required for restoring a backup.
4. Described these improvements for the user.

Image backup commands were tested with local and NFS image storage. The metadata backup command was tested by running it directly on a DTR node and through a UCP client bundle with multiple replicas.

* Technical and editorial review

* More edits

docker/docker.github.io,thaJeztah/docker.github.io,docker/docker.github.io,thaJeztah/docker.github.io,thaJeztah/docker.github.io,docker/docker.github.io,docker/docker.github.io,thaJeztah/docker.github.io,docker/docker.github.io,thaJeztah/docker.github.io