Bug 20900: Add CPL test branch in rollingloans.t

Bug 20900: Add CPL test branch in rollingloans.t

Trivial fix.

Test plan:
Without this patch and a CPL library, run rollingsloans.t. See warns.
With this patch, no warns.

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
(cherry picked from commit 7e3f399867abdf506ff271c57d652d1b3cdf8a7e)
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>