CQLSH: wait up to 10 sec for a tracing session.

patch by Mikhail Stepura; reviewed by Tyler Hobbs for CASSANDRA-7222
Merge branch 'cassandra-2.0' into cassandra-2.1.0
Merge branch 'cassandra-2.1.0' into cassandra-2.1
Merge branch 'cassandra-2.1' into trunk