While the progress dots during the copying of the store work fine on a
normal terminal, those look pretty off if the script is run inside a
provisioning script of e.g. `vagrant` or `packer` where `stderr` and
`stdout` are captured:
default: .
default: ..
default: .
default: .
default: .
To work around this, the script checks with `-t 0` if it's
running on an actual terminal and doesn't show the progress if that's not
the case.
(cherry picked from commit d9367a2dd1)
85329cac35