Fixup CMakeLists.txt

Made the tests binary names consistent by using - and not _

Change-Id: I30701fee272f582e4cb9499df8c1ec0755956bd7
Reviewed-on: http://review.couchbase.org/34931
Tested-by: buildbot <build@couchbase.com>
Reviewed-by: Trond Norbye <trond.norbye@gmail.com>