util: remove unused the service fd constant
parasite: stop task on the exit point from sigreturn
parasite_stop_on_syscall
parasite: add simplified version of parasite_prep_ctl

It will be used for unmaping restorer blob.
parasite: add a function for unmaping bootstrap blob
close_service_fd(CR_PROC_FD_OFF)
Prepare for unmaping restorer blobs from restored tasks
restore: parasite_stop_on_sigreturin
restore: save task state on pstree_item
restore: don't determine real pid for the root task
restorer: unmap itself
parasite: unmap itself
debug