Introduce validation logic to `ark restore logs`
Introduce validation logic to `ark restore logs`

This commit introduces validation logic to `ark restore logs`
command, the way it already exists in other commands like `ark
restore create`.

Before the logs for a restore are fetched from the server, the
server is contacted to check if the specified restore exists. If
it does not, it errors out.

Fixes #389

Signed-off-by: Shubham <c250f88274cb8a75961a08502efcb7c262033c87@linux.com>

heptio/ark,heptio/ark