Bug 28336: Add missing input for item_action

Bug 28336: Add missing input for item_action

To test:
1 - Stage a marc file of authorities
2 - Manage the staged file
3 - Attempt to change the matching rule
4 - 500 Error, in intranet-error.log:
[Wed May 12 16:53:03.046652 2021] [cgi:error] [pid 52072] [client 172.19.0.1:50580] AH01215: C4::ImportBatch::SetImportBatchItemAction(): DBI Exception: DBD::mysql::st execute failed: Column 'item_action' cannot be null [for Statement "UPDATE import_batches SET item_action = ? WHERE import_batch_id = ?" with ParamValues: 0=undef, 1="1"] at /kohadevbox/koha/tools/manage-marc-import.pl line 160: /kohadevbox/koha/tools/manage-marc-import.pl, referer: http://localhost:8081/cgi-bin/koha/tools/manage-marc-import.pl?import_batch_id=1
5 - Apply patch
6 - Reload page and change matching rule
7 - Success!

Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>