(ITS#8393) LMDB - MDB_GET_BOTH broken on non-dup value

[hyc@openldap.org]

Full_Name: Howard Chu
Version: 0.9.18
OS: Linux
URL: ftp://ftp.openldap.org/incoming/
Submission from: (NULL) (78.155.228.110)
Submitted by: hyc


Using mdb_cursor_get(MDB_GET_BOTH) doesn't return the data item if the record is
not a dup (i.e., there's only a single value under the key) even though it
matches. 

This doesn't affect slapd because (1) when we use this command, the key always
has more than 1 value and (2) when we use it, the data item we passed in is
exactly the same as what we would get returned, on a match.

This affects other apps where both (1) and (2) are not true, e.g. a compare
function is used that only compares a subset of the data, in order to retrieve
the full record.