Bring the LDAPCacheEntries and LDAPOpCacheEntries usage() in synch with

the manual and the implementation (0 and -1 both disable the cache).

PR 40948


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@814441 13f79535-47bb-0310-9956-ffa450edef68