Redirect upload step

[enderahmetyurt]

Fix #1322

[Shpigford]

I agree with the bug, but we likely need a bit more nuance to where this redirects.

There's an uploaded? method on the Import model that checks for an uploaded file so maybe we need some sort of if/else or case statement to check for the current step and redirect to the appropriate one?

[enderahmetyurt]

Good point @Shpigford. How does it look now?

[Shpigford]

@enderahmetyurt Works for me! Thanks!