enable ssl + ssl_verify_server_cert in the internal client too
* fix replication tests to disable master_ssl_verify_server_cert
because accounts are passwordless - except rpl.rpl_ssl1
* fix federated/federatedx/connect to disable SSL_VERIFY_SERVER_CERT
because they cannot configure an ssl connection
* fix spider to disable ssl_verify_server_cert, if configuration
says so, as spider _can_ configure an ssl connection
* memory leak in embedded test-connect
Parallel slave server shutdown found to be hanging in
close_connections() triggered by shutdown due to a slave worker thread
would not be notified to exit in case the worker was sitting idle.
Fixed with destroying the worker pool earlier that is in
slave_prepare_for_shutdown() when all their driver threads have already left.
A test file is added to simulate the bug condition as well as check
multi-sourced and not-idle worker cases.
