(ITS#4793) connection_get race condition on Windows

[hyc@OpenLDAP.org]

Full_Name: Howard Chu
Version: HEAD
OS: Windows XP
URL: ftp://ftp.openldap.org/incoming/
Submission from: (NULL) (76.168.84.21)
Submitted by: hyc


test039 was consistently failing in an assert() in slapd_set_read() called from
connection_read(). The problem was that connection_get() was returning a
connection structure that got closed and immediately reused. The problem may
also be in RE23 since they're using the same connection manager now, but I
haven't built RE23 on Windows recently to verify.