LU-5862 changelog: Proper record remapping

Fixed changelog_remap_rec() to correctly remap records emitted
with jobid_var=disabled, i.e. delivered by new servers but with
no jobid field.

Updated sanity test 205 accordingly.

Signed-off-by: Henri Doreau <henri.doreau@cea.fr>
Change-Id: Ia151e9bfde2def8819913ee658bde6b71ef3ab18
Reviewed-on: http://review.whamcloud.com/12574
Tested-by: Jenkins
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Robert Read <robert.read@intel.com>