Fixed potential class pool override in integration tests.

Fixed potential class pool override in integration tests.

Classloader in JUnit test is shared resource and in order
to integrate well with Javassist we are required to share
also classpool in order to compile generated code
using previously existing generated code in same Classloader.

If we introduce new ClassPool for same classloader,
compilation may fail, because new ClassPool is unable
to fetch bytecode for already generated classes.

Change-Id: Idd933670fe0a1c06d40aeed182f46997a843ab91
Signed-off-by: Tony Tkacik <ttkacik@cisco.com>