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>
(cherry picked from commit 1017edad1c27d2624fb8ed6f8fb0018985b33295)
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
(cherry picked from commit 18ad4150eadff0f229c1cc73950f8e53568ed249)
Signed-off-by: Julian Maurice <julian.maurice@biblibre.com>