LP#1491875: avoid erroneous "unsaved data" popup during MARC record creation

LP#1491875: avoid erroneous "unsaved data" popup during MARC record creation

Test plan
---------
[1] Navigate to Cataloging -> Create New MARC Record.
[2] Choose a template, click Load
[3] Enter data in a fixed field, for example, Date1
[4] Enter data in a MARC field such as 100
[5] Click Create Record:

    The "This tab may have unsaved data. ..." pop up will appear.
    Clicking OK will save the record and take the user to their default
    view of the record.
    Clicking Cancel will save the record and return the user to the MARC
    Edit screen.
    The behavior when clicking Cancel can lead to confusion as to
    whether the record has actually been saved.

[6] Apply the patch and repeats steps #1-#5.
[7] This time, no extraneous unsaved data warning should appear.

Note that this patch's kludge doesn't fix all possible instances
of the warning; see https://bugs.launchpad.net/evergreen/+bug/1491875/comments/6
for details.

Signed-off-by: Jason Etheridge <jason@esilibrary.com>
SIgned-off-by: Andrea Neiman <abneiman@equinoxinitiative.org>
Signed-off-by: Galen Charlton <gmc@equinoxinitiative.org>