Bug 13606 Clear job data in session when the job is completed

Bug 13606 Clear job data in session when the job is completed

Bug 11395 uses the session to store the report sent to the interface
(update on biblio XX OK, etc.).

If the session is stored in mysql, the max size of the
sessions.a_session will be reached easily (TEXT field).

To reproduce:
0/ Set SessionStorage to 'mysql'
1/ Create a file with 500 biblionumbers:
  mysql -e "select biblionumber from biblio limit 500;" | tail -n 500 > /tmp/biblionumbers.txt
2/ Define a marc modification template (something like "delete field 99$9" is nice)
3/ Load the /tmp/biblionumbers.txt in the batch biblio modification tool
4/ Repeat 3
You will get:
  Syck parser (line 1534, column 6): syntax error at
  /usr/lib/i386-linux-gnu/perl5/5.20/YAML/Syck.pm line 75.
None Koha page is reachable.

It comes from get_template_and_user > checkauth > get_session >
l.1595 $session = new CGI::Session("driver:MySQL;serializer:yaml;id:md5", $sessionID, {Handle=>$dbh});

5/ Get your sessionID contained in your CGISESSID cookie
Have a look at the value a_session in the sessions table:
mysql> select a_session from sessions where id="YOUR_SESSIONID";

You should see that the yaml is not correctly ended.
The size of the DB field has been reached and the yaml is truncated.

Test plan:
0/ Delete your CGISESSID cookie
1/ Try to reproduce the previous issue
2/ After the second batch, have a look at the sessions table and confirm
that only one job_$JOB_ID exist in the yaml

Signed-off-by: Jonathan Druart <jonathan.druart@biblibre.com>
NOTE: Nicely clears batch job session information.
      (2) is incorrect. This cleans up after a full run.

Signed-off-by: Mark Tompsett <mtompset@hotmail.com>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>