rtpvp8depay: Add property for waiting until the next keyframe after packet loss

If VP8 is not encoded with error resilience enabled then any packet loss
causes very bad artefacts when decoding and waiting for the next
keyframe instead improves user experience considerably.
21 jobs for vp8depay-wait-for-keyframe in 86 minutes and 34 seconds (queued for 4 seconds)
Status Job ID Name Coverage
  Preparation
passed #498145
gst indent

00:00:40

passed #498144
manifest

00:00:47

 
  Build
passed #498151
build cerbero android universal

00:21:35

passed #498152
build cerbero cross win32

00:05:06

passed #498153
build cerbero cross win64

00:05:30

passed #498150
build cerbero fedora x86_64

00:12:54

manual #498155
gst-ios-12.2 allowed to fail manual
build cerbero ios universal
passed #498154
gst-macos-10.14
build cerbero macos x86_64

00:08:02

passed #498146
build fedora x86_64

00:06:59

passed #498147
build nodebug fedora x86_64

00:13:35

passed #498148
build static fedora x86_64

00:10:44

passed #498149
build static nodebug fedora x86_64

00:13:21

 
  Test
passed #498702
check fedora

00:04:40

passed #498157
integration testsuites fedora

00:50:50

passed #498159
valgrind bad

00:15:05

passed #498703
valgrind ges

00:07:14

passed #498158
valgrind good

00:20:40

failed #498156
check fedora

00:07:48

failed #498160
valgrind ges

00:14:23

 
  Integrate
passed #498161
android universal examples

00:06:04

passed #498162
documentation

00:03:36