CBQE-0: revert 350e07e

https://github.com/couchbase/testrunner/commit/350e07ea84a049517bc00511e668dbb21024f02c
1) we don't wait self._async_load_all_buckets completed -> data is loaded even after failure
2) start_time is not defined

Change-Id: Ib308578e2ff3aeb7c1a7c3d11c12a580dbc96239
Reviewed-on: http://review.couchbase.org/36825
Tested-by: buildbot <build@couchbase.com>
Reviewed-by: Andrei Baranouski <andrei.baranouski@gmail.com>