Bug 18736: (QA follow-up) Cosmetic changes

Bug 18736: (QA follow-up) Cosmetic changes

[1] Resolve warnings like:
Use of uninitialized value $rounding_pref in string eq at /usr/share/koha/devclone/C4/Acquisition.pm line 2040.

[2] Fixing unusual use of whitespace too.

[3] Remove list operator from get_rounding_sql return. Only used in scalar
context.

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
(cherry picked from commit 9922d2bf40e2b7429f300d4d73134f9fef3b8c65)
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>