cassini-[distro,tests]: Add `jfrog-cli` to image for `cassini-test`

JFrog is used to share the artifacts between Gitlab CI and LAVA. Add
`jfrog-cli` package to the image when `cassini-test` distro feature
is enabled.

Signed-off-by: Devaraj Ranganna <devaraj.ranganna@arm.com>