CBQE-0: revert I2c6791 remove sleep 30 sec after bucket creation

revert https://github.com/couchbase/testrunner/commit/b1db14049a345f09bfdf895b6169112e4c22b2db
see Junyi's comment mhttp://review.couchbase.org/#/c/31240/ also

Change-Id: Ib58c5ed7601512f98f0c05d1cdf78481d99febb3
Reviewed-on: http://review.couchbase.org/31545
Reviewed-by: Andrei Baranouski <andrei.baranouski@gmail.com>
Tested-by: Andrei Baranouski <andrei.baranouski@gmail.com>