Bug 21620: Prevent stockrotation cronjob failures

Bug 21620: Prevent stockrotation cronjob failures

Superflous use of sprintf combined with rebasing issue left the
stockrotation cronjob such that a 'No action taken' email report would
catastrophically fail with the error:

Redundant argument in sprintf at ./stockrotation.pl line 316

This patch both resolves the error and cleans up some additional
unrequired sprintf usage.

Test Plan
1) Create a rotation plan
2) Add some items to the rotation plan
3) Run the cronjob using `stockrotation.pl --report=email --send-email
--execute`
4) Note the lack of errors

Signed-off-by: Mark Tompsett <mtompset@hotmail.com>
Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>