BUG-893: do not use deprecated contructor

This gets rid of using JavassistUtils' deprecated contructor. It also
removes storage of ClassPool, so it makes it easier to reason about it.

Change-Id: I2deb15e7ce85527bdfb7fb79ae46bb5d25466ca2
Signed-off-by: Robert Varga <rovarga@cisco.com>
(cherry picked from commit c3456331e78096eb6e3834ace5b60f9f5972bbb1)
Signed-off-by: Robert Varga <rovarga@cisco.com>
Merge "BUG-893: do not use deprecated contructor" into stable/hydrogen