More for #7589
ITS#7735 plug memleak

Introduced in commit 48cdd54d9accb9283807ed592369b72654fb302d
Fix slap_reparse_sync_cookie prototype
ITS#7735
ITS#7740 back-meta: avoid blocking other threads

Don't lock other threads while trying to connect to remote node.
ITS#7740
ITS#7739 fix for empty nested include
ITS#7739
Merge remote-tracking branch 'origin/mdb.master' into OPENLDAP_REL_ENG_2_4
More for ITS#7589
ITS#7735 fix memctx usage in prev commit
Fix CONFIG_DELETE crash

Closing a connection can abandon its ops without going thru the threadpool,
so make sure to lock the si_ops_mutex before walking the list.
ITS#7741 Fix entryDN index lookup

DN notfound is authoritative, don't ignore the result
ITS#7741