[dw-free] Entry preview shows the wrong user when browser autofills username/password

[fu]

[commit: http://hg.dwscoalition.org/dw-free/rev/0a49a231ba1a]

http://bugs.dwscoalition.org/show_bug.cgi?id=3202

This field may have been filled by browser autofill, so check that we meant
to login as another user before deciding that we are previewing as that
user.

Patch by fu.

Files modified:

• htdocs/js/entry.js
• htdocs/preview/entry.bml

( Diff: 2 files changed. )