Add test-valgrind to run the testsuite under valgrind

Change-Id: I5c173d8d264cf3ac15621a5574f0b9eac7bfcd44
Reviewed-on: http://review.couchbase.org/33978
Reviewed-by: Trond Norbye <trond.norbye@gmail.com>
Tested-by: Trond Norbye <trond.norbye@gmail.com>