Ticket 47592 - automember plugin task memory leaks
The search pblock was not destroyed at the end of the export and rebuild
tasks.
https://fedorahosted.org/389/ticket/47592
Reviewed by: richm(Thanks!)
(cherry picked from commit 085c6d494f90231f2e572a668ab601c321bffb01)
(cherry picked from commit c9c7d545a987f8f52c9752ba1181d1885b74480c)