Fix %f conversion in bsnprintf.

Signed-off-by: Marco van Wieringen <marco.van.wieringen@bareos.com>
Fix conversion string in bsnprintf.

It makes no sense to use a string "0123456789ABCDEF" when you do
all calculating using a modulo 10 divide which only gives the spread
from 0 to 9. As we don't need the hex letters we can also drop the check
on caps as figures are either upper or lower case.