Bug 22237: Subscriptions are not linked to Mana upon edit

Bug 22237: Subscriptions are not linked to Mana upon edit

This patch modifies C4/Serials.pm so that during the process of editing
a subscription a link to Mana can be created.

To test, apply the patch and go to Serials.

 - Locate a subscription which was not created using Mana data but which
   can be found in Mana.
 - Edit the subscription, skipping to the second page.
 - View the results returned by Mana and select one.
 - Save the subscription.
 - Upon being redirected to the subscription detail page you should see
   a "Report mistake" button. This shows that the subscription has been
   linked to Mana successfully.

Signed-off-by: Josef Moravec <josef.moravec@gmail.com>
Signed-off-by: Alex Arnaud <alex.arnaud@biblibre.com>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>