Bug 697027 - 3 - minor memory leaks found by Valgrind + TET
https://bugzilla.redhat.com/show_bug.cgi?id=697027
Description: Adding slapi_counter_destroy to destroy counters
cache->c_cursize, c_hits, and c_tries used in the entry cache.
Additionally, changing to make cache_init fail if slapi_counter
is not enabled since cache->c_cursize depends upon the counter
and the cache module cannot function unless c_cursize is available.