Problem:
========
Audit plugins are being acquired on the first use. Releasing plugins after execution
of each query and reacquiring them again significantly affects scalability.

Fix:
====
Audit plugins are being acquired on the first use, and released when the connection ends.

Reviewed-by:
============
Georgi Kodinov <georgi.kodinov@oracle.com>
Ramil Kalimullin <ramil.kalimullin@oracle.com>