fix oc_timer issue

if the next timer is deleted by current timer's callback function,
the timer list is broken.
4 jobs for master in 9 minutes and 4 seconds (queued for 3 seconds)
Status Job ID Name Coverage
  Build
passed #2910
Android_build

00:08:31

passed #2911
doxygen

00:00:58

passed #2908
Linux_Secured_Test

00:03:12

passed #2909
Linux_Unsecured_Test

00:02:48