Issue 49188 - retrocl can crash server at shutdown
Description: We do not calloc enough elements when processing nsslapd-attribute
from the retrocl plugin configuration. This causes invalid memory
to be freed at shutdown(via slapi_ch_array_free).
https://pagure.io/389-ds-base/issue/49188
Reviewed by: mreynolds(one line commit rule)
(cherry picked from commit b2f76abe10bfbe621308410a1e7f41287cf2ff9e)