Fixed [#11] Sending not needed 'USE <ks>' to new CQL hosts.

For details see: #11

2.9.0-yb-10

Fix potential deadlock invoking Session::refresh_metadata_callback

Fixed several data races.

#1837: Fixed TSAN issues in C++ driver in PartitionAwarePolicy.

Summary:
Reworked updating of partitions in the metadata object for PartitionAwarePolicy:
 - the partitions updating timer (PeriodicTask) was moved from PartitionAwarePolicy into Session object. (Using Session's event loop.)
 - Instead of internal `ControlMultipleRequestCallback::execute_query` now using `Session::execute ` async API.

Test Plan: ybd tsan --cxx-test integration-tests_cassandra_cpp_driver-test --gtest_filter CppCassandraDriverTest.BatchWriteDuringSoftMemoryLimit

Reviewers: mikhail

Reviewed By: mikhail

Subscribers: yql

Differential Revision: https://phabricator.dev.yugabyte.com/D9241

2.9.0-yb-6

Add YB hash code to C interface