CBQE-0: fix cbhealthchecker tests

fix number of items to check

Change-Id: I7472fc5d297737989d27dbb15a1ab5d37f091c4e
Reviewed-on: http://review.couchbase.org/32991
Reviewed-by: Iryna Mironava <irynamironava@yandex.ru>
Tested-by: Iryna Mironava <irynamironava@yandex.ru>