Implemented ConnectionPool.executeCQLAllClients(), which does what
the name suggests it does. Put this to work in the cql2 and cql3
test suites to make all pool clients use the test keyspace. This
has the salutary effect of allowing all the tests to pass if
a) you're testing against a pool of size > 1, and b) that pool
points to a cassandra ring with more than one keyspace.

Also, bumped up the ping interval to 30 seconds.