Bug 18807: Fix tests www/batch.t

Bug 18807: Fix tests www/batch.t

Several things are wrong here:
1. It assumes that import_record_id is the biblionumber
=> Wrong, it is only true when the DB is empty and that the 2 AI equal 1
2. The encoding in the template is 'UTF-8', not 'utf8', it leaded to
  "stage-marc-import.pl: marc21record.mrc: Unexpected charset UTF-8, expecting utf8"
3. We did not test that the biblio was correctly imported

Test plan:
Make sure the tests now pass.
For the www tests you need to set the following env vars:
KOHA_USER, KOHA_PASS, KOHA_INTRANET_URL and KOHA_OPAC_URL

Signed-off-by: Lee Jamison <ldjamison@marywood.edu>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>