Fixes glance_url to use a string, not a text field

This updates db/seeds.rb only, without a migration. But since we're
updating before the release, there should be need for one.

It turns out that :type => 'text' gives you a textarea...

Closes https://github.com/aeolusproject/conductor/issues/335
Merge pull request #356 from n1zyy/issue335-glance_url_huge

Fixes glance_url to use a string, not a text field