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: 372b97c27d60b34a6148744b524675eb14b315f1
kmuzalewska/j-pet-framework,kmuzalewska/j-pet-framework,kmuzalewska/j-pet-framework,kmuzalewska/j-pet-framework,kmuzalewska/j-pet-framework