Allow env var override of perf test target time
Updated jub-effort.txt for c3.xlarge
Increase HBase and Cassandra timeouts in testing

Changed CONNECTION_TIMEOUT_KEY from 10s to 60s for Cassandra and HBase
tests.  This was motivated by performance testing on EC2, where
truncating column families on Cassandra could take over ten seconds
after many iterations of the same test method (truncating CFs after
each run).  I'm not sure why this operation was slow, but since it's
just CF truncation in clearStorage() and so far does not appear to
affect querying, I'm just going to bump up the timeout.  The 60s value
made the timeouts disappear on an EC2 c3.xlarge.