In some cases the 'reschedule' code path is executed when the current
thread is the same as the next thread in the ready Q. If this happens,
the swap_return_value of the thread is ifalsely being reset to -EAGAIN.
This commit prevents the rescheduling code to run if the current thread
is the same as the thread in the ready Q.
Signed-off-by: Wolfgang Reißnegger <gnagflow@fb.com>