rtpjitterbuffer: Don't use stats timer on the timers queue

The timer passed to update_timers may be from the stats timer. At the
moment, we could endup rescheduling (reusing) that timer onto the normal
timer queue, unschedul it as if it was from the normal timer queue or
duplicate it into the stats timer queue again. This was protected before
as the with the fact the stats timer didn't have a valid idx.
20 jobs for jitterbuffer-timer-reschedule in 67 minutes and 12 seconds (queued for 3 seconds)
Status Job ID Name Coverage
  Preparation
passed #418510
gst indent

00:00:22

passed #418509
manifest

00:00:29

 
  Build
passed #418516
build cerbero android universal

00:23:43

passed #418517
build cerbero cross win32

00:10:28

passed #418518
build cerbero cross win64

00:06:21

passed #418515
build cerbero fedora x86_64

00:14:04

manual #418520
gst-ios-12.2 allowed to fail manual
build cerbero ios universal
passed #418519
gst-macos-10.14
build cerbero macos x86_64

00:06:49

passed #418511
build fedora x86_64

00:17:43

passed #418512
build nodebug fedora x86_64

00:14:39

passed #418513
build static fedora x86_64

00:32:31

passed #418514
build static nodebug fedora x86_64

00:29:18

 
  Test
passed #418622
check fedora

00:03:25

passed #418522
integration testsuites fedora

00:10:57

passed #418524
valgrind bad

00:13:02

passed #418525
valgrind ges

00:04:04

passed #418523
valgrind good

00:20:03

failed #418521
check fedora

00:06:02

 
  Integrate
passed #418526
android universal examples

00:10:19

passed #418527
documentation

00:05:09