Comment 4 for bug 1760223

I've tested this as indicated above and the fix works as expected on webstaff using latest Chrome: I see the MARCXML download as a file, and not to the page as txt.

Here's a signoff branch with the current signoffs

http://git.evergreen-ils.org/?p=working/Evergreen.git;a=shortlog;h=refs/heads/user/cesardv/miker_lp-1760223-download-exported-records_signoff