CBQE-0: remove lib/testrunner_common.py

it's old module for membase, never used

Change-Id: I642d3ea1b90a18a675acfdc2c941a53c1e168910
Reviewed-on: http://review.couchbase.org/34819
Reviewed-by: Andrei Baranouski <andrei.baranouski@gmail.com>
Tested-by: Andrei Baranouski <andrei.baranouski@gmail.com>