In JPetManager destructor add cleaning of param caches.
In JPetManager destructor add cleaning of param caches.

Not sure if it is necessary. Also, add check if executor not empty
and then delete executor.


Former-commit-id: cba4c510cdd9569751e047fe75e4ebe724c91f36
kmuzalewska/j-pet-framework,kmuzalewska/j-pet-framework,kmuzalewska/j-pet-framework,kmuzalewska/j-pet-framework,kmuzalewska/j-pet-framework