Dvc: More verbose output after dvc push to SSH remote

[robguinness]

After running dvc push to an SSH remote, even with the verbose flags maxed out (-vvv), there is no output for awhile after dvc requests the credentials for the remote. This leads the user (at least in my case) to suspect a problem with SSH authentication when in reality dvc is working on something else (according to @efiop this is the case).

It would be nice to have more verbose info printed to the console. For example, "SSH authentication suceeded. Now doing _XXX_...". In my opinion, especially when using -vvv, the user should always have an idea what dvc is actually trying to do.

[ei-grad]

If it hangs on "Collecting information" state, then this is the problem with the status gathering, which would have a progress bar when #1804 would be merged.

This is how it looks now: https://asciinema.org/a/EGhX3N5R0bmfc47oczTXyNBxJ
And how it would be looking: https://asciinema.org/a/oE5kPygW3J8vktnPocGB6pv8B

[ei-grad]

Though it still could "hang" in the scenario when the current repository needs a small amount of files from the remote which has a huge amount of files. For this case DVC should not only notice the ssh auth success, but suggest no_traversal = true to be specified.

[efiop]

@ei-grad Wow, that looks amazing! :fire: :fire: :fire: