Kernel: Fix Process::exit() and where it is called from

cksum doesn't seem to work anymore on big files. I have to look
into this. It locks up after couple of seconds...

kernel/kernel/Scheduler.cpp

@@ -245,7 +245,8 @@ namespace Kernel
 
 	void Scheduler::set_current_process_done()
 	{
-		VERIFY_CLI();
+		VERIFY_STI();
+		DISABLE_INTERRUPTS();
 
 		pid_t pid = m_current_thread->thread->process().pid();
 
@@ -253,6 +254,7 @@ namespace Kernel
 		remove_threads(m_sleeping_threads, it->thread->process().pid() == pid);
 		remove_threads(m_active_threads, it != m_current_thread && it->thread->process().pid() == pid);
 
+		delete &m_current_thread->thread->process();
 		delete m_current_thread->thread;
 		remove_and_advance_current_thread();
 		execute_current_thread();