ticket https://fedorahosted.org/389/ticket/47976

fix https://fedorahosted.org/389/attachment/ticket/47976/0001-Ticket-47976-deadlock-in-mep-delete-post-op.patch

test case: https://fedorahosted.org/389/attachment/ticket/47976/0002-Ticket-47976-test-case.patch