Add unregisterProcess function in class UserKernel
Add unregisterProcess function in class UserKernel

bngabonziza/CS162,thinkhy/CS162,bngabonziza/CS162,yl2695/CS162,yl2695/CS162,bngabonziza/CS162,yl2695/CS162,bngabonziza/CS162,yl2695/CS162,bngabonziza/CS162,thinkhy/CS162,thinkhy/CS162,thinkhy/CS162,yl2695/CS162