(ITS#5094) shutting down multiple ppolicy instances yields double-free

[mbackes@symas.com]

Full_Name: Matthew Backes
Version: 2.3.x, head
OS: all
URL: 
Submission from: (NULL) (132.241.73.19)


slapo-ppolicy's close method frees the static pwcons without checking to see if
someone else is using or has freed it already.

This issue appears at shutdown when trying to use slapo-ppolicy on multiple
backends.

Revisions 1.105 and 1.106 to ppolicy.c (in HEAD) fix this problem.