Bug 15030 - Fixes the serials fields associated with a plugin, to not overwrite the...

Bug 15030 - Fixes the serials fields associated with a plugin, to not overwrite the previously saved value

This fixes the remaining fields from serials-edit.pl that were seeing their previously entered values
be oblitarated with each new edit.  The fields associated to a plugin (dateaccessioned and barcode) were
always displaying <empty> with each new edit, losing the previous effort.

Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Josef Moravec <josef.moravec@gmail.com>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>