Deprecates --volume-id arg for v2 backup-restore

This patch deprecates the --volume-id arg of backup-restore
when using the v2 api and adds (preferred) --volume arg.
Both args are still usable but the former is now listed as
"Deprecated" in the help message.

Change-Id: I2575d93041b26f971c59bc04828b356556617b62
Fixes: bug 1242816