Process only the jobs initially registered on the processing list. This
makes it possible to add jobs for the current processor in a job
handler. These jobs are processed with the next
SMP_MESSAGE_PERFORM_JOBS message. The lock is only acquired and
released once.
Move resposibility to disable thread dispatching to the caller of
_SMP_Multicast_action(). Using an interrupt disable for this purpose is
questionable.
If the caller already disabled interrupts, then do not disable thread
dispatching. Calling _SMP_Multicast_action() with interrupts disabled
is a questionable use case.
