Bug 16373: merge.pl reports success but files are not merged

Bug 16373: merge.pl reports success but files are not merged

To recreate:

1) Select two biblios to merge
2) Merge them
3) Sucess reported but list of bibs contains only the reference record.
4) View the 'new' record, it won't have any additional items
5) View the 'merged' record, it is still there with its items

This happens because record IDs (biblionumbers) are not correctly
set up in the template on the 2nd merge stage, since Bug 15358.

To test:

1) apply patch
2) try to recreate this issue once again, confirm that a problem
is resolved

Signed-off-by: Chris Cormack <chris@bigballofwax.co.nz>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Brendan Gallagher <brendan@bywatersolutions.com>