Task's state update when tpl_start() is called

[khaoulaboukir]

Hello,

When tpl_start() is called (file : tpl_os_kernel.c) to start a task and the task's state is "READY_AND_NEW" then we need to :

1. Intialize its descriptor
2. Change its state to "READY".

Currently the change of state is done only when the number of cores is greater than one (line 738 to 740 of tpl_os_kernel.c file), however I think we need to do it also for the single-core case.