(ITS#4406) proxycache crashes on attrsonly searches

[hyc@OpenLDAP.org]

Full_Name: Howard Chu
Version: HEAD/2.3
OS: 
URL: ftp://ftp.openldap.org/incoming/
Submission from: (NULL) (63.193.240.128)
Submitted by: hyc


If a search that matches a proxycache template arrives but has attrsonly set
TRUE, the overlay will attempt to cache the resulting entries but there are no
values to store. If any of the attributes are indexed there will be an assert
failure in the indexer due to the lack of any values. The overlay should not
attempt to cache any queries with attrsonly set TRUE.