MINOR: task/profiling: do not record task_drop_running() as a caller

MINOR: task/profiling: do not record task_drop_running() as a caller

Task_drop_running() is used to remove the RUNNING bit and check if
while the task was running it got a new wakeup from itself. Thus
each time task_drop_running() marks itself as a caller, it in fact
removes the previous caller that woke up the task, such as below:

Tasks activity over 10.439 sec till 0.000 sec ago:
  function                      calls   cpu_tot   cpu_avg   lat_tot   lat_avg
  task_run_applet            57895273   6.396m    6.628us   2.733h    170.0us <- run_tasks_from_lists@src/task.c:658 task_drop_running

Better not mark this function as a caller and keep the original one:

Tasks activity over 13.834 sec till 0.000 sec ago:
  function                      calls   cpu_tot   cpu_avg   lat_tot   lat_avg
  task_run_applet            62424582   5.825m    5.599us   5.717h    329.7us <- sc_app_chk_rcv_applet@src/stconn.c:952 appctx_wakeup