rtpjitterbuffer: Clear clock master before unreffing

Make sure to clear any master clock on the media_clock
before unreffing it to release the timer callback that's
updating the clock and keeping it reffed.
20 jobs for rtpjitterbuffer-clear-clock-master in 35 minutes and 28 seconds (queued for 5 seconds)
Status Job ID Name Coverage
  Preparation
passed #362359
gst indent

00:00:31

passed #362358
manifest

00:00:39

 
  Build
passed #362365
build cerbero android universal

00:12:36

passed #362366
build cerbero cross win32

00:09:08

passed #362367
build cerbero cross win64

00:06:13

passed #362364
build cerbero fedora x86_64

00:09:01

manual #362369
gst-ios-12.2 allowed to fail manual
build cerbero ios universal
passed #362368
gst-macos-10.14
build cerbero macos x86_64

00:08:31

passed #362360
build fedora x86_64

00:09:18

passed #362361
build nodebug fedora x86_64

00:08:10

passed #362362
build static fedora x86_64

00:13:18

passed #362363
build static nodebug fedora x86_64

00:13:09

 
  Test
passed #362379
check fedora

00:03:16

passed #362371
integration testsuites fedora

00:10:29

passed #362373
valgrind bad

00:11:46

passed #362374
valgrind ges

00:05:10

passed #362372
valgrind good

00:09:03

failed #362370
check fedora

00:09:03

 
  Integrate
passed #362375
android universal examples

00:06:26

passed #362376
documentation

00:04:09