ENG-6930: Fix a boolean polarity issue in the JDBC driver.

(cherry picked from commit 35a7bfa351f5ac8d3c4684ba5c3c900d191c9fef)
ENG-6915: When connecting a new client in the JDBC driver, call
close() on the client if it doesn't connect to the cluster to avoid
leaking threads.

(cherry picked from commit 2db97d460251134edeb3d51cca264a4b9c79383c)