rtpjitterbuffer: make sure not to drop packets based on skew

One of the jitterbuffers functions is to try and make sense of weird
network behavior.

It is quite unhelpful for the jitterbuffer to start dropping packets
itself when what you are trying to achieve is better network resilience.

In the case of a skew, this could often mean the sender has restarted
in some fashion, and then dropping the very first buffer of this "new"
stream could often mean missing valuable information, like in the case
of video and I-frames.

This patch simply reverts back to the old behavior, prior to gstreamer/gst-plugins-good@8d955fc3
and includes the simplest test I could write to demonstrate the behavior,
where a single packet arrives "perfectly", then a 50ms gap happens,
and then two more packets arrive in perfect order after that.

# Conflicts:
#	tests/check/elements/rtpjitterbuffer.c
24 jobs for jitterbuffer-dont-drop-skew-packets in 69 minutes and 57 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Preparation
failed #779113
gst indent

00:00:47

passed #779112
manifest

00:00:30

 
  Build
passed #779123
build cerbero cross-android universal

00:21:58

manual #779127
gst-ios-12.2 allowed to fail manual
build cerbero cross-ios universal
passed #779124
build cerbero cross win32

00:10:56

passed #779125
build cerbero cross win64

00:06:13

passed #779122
build cerbero fedora x86_64

00:05:47

passed #779126
gst-macos-10.14
build cerbero macos x86_64

00:08:02

passed #779118
build clang fedora x86_64

00:07:52

passed #779114
build fedora x86_64

00:09:24

failed #779121
1607 windows docker
build msys2

00:05:17

passed #779115
build nodebug fedora x86_64

00:04:30

passed #779116
build static fedora x86_64

00:10:33

passed #779117
build static nodebug fedora x86_64

00:08:27

passed #779119
1607 windows docker
build vs2017 amd64

00:11:03

passed #779120
1607 windows docker
build vs2017 x86

00:11:02

 
  Test
passed #779128
check fedora

00:03:52

failed #779129
integration testsuites fedora

01:00:00

passed #779131
valgrind bad

00:10:11

passed #779132
valgrind ges

00:13:58

passed #779130
valgrind good

00:20:11

 
  Integrate
passed #779133
cross-android universal examples

00:08:05

skipped #779135
gst-ios-12.2 allowed to fail manual
cross-ios universal examples
passed #779134
documentation

00:03:58

 
Name Stage Failure
failed
integration testsuites fedora Test The script exceeded the maximum execution time set for the job
  |  Prerolling...
| Pipeline started
|
| Executing set-vars (
| - default_flags=flush
| )
| <position: 0:00:00.000000000 duration: 0:00:10.000000000 speed: 1.000000 />
| <position: 0:00:00.000000000 duration: 0:00:10.000000000 speed: 1.000000 />
| <position: 0:00:00.000000000 duration: 0:00:10.000000000 speed:
Job's log exceeded limit of 4194304 bytes.
failed
build msys2 Build
Checking out 30672ba7d134553e59935ddc875104adba26f25c in gst-plugins-base
-> 30672ba - meson: build gir even when cross-compiling if introspection was enabled explicitly
Checking out 44788e00688e9673e550b00ccdcb79f3d4faa83b in gst-plugins-good

Could not rebase subprojects\gst-plugins-good, please fix and try again. Error:

fatal: reference is not a tree: 44788e00688e9673e550b00ccdcb79f3d4faa83b
Command '['git', 'checkout', '--detach', '44788e00688e9673e550b00ccdcb79f3d4faa83b']' returned non-zero exit status 128.
ERROR: Job failed: exit code 1
failed
gst indent Preparation
   for (i = 0; i < 2; i++) {
gst_harness_push (h, generate_test_buffer_full (now + i * GST_MSECOND * 20,

- base_seqnum + i, (base_seqnum + i) * TEST_RTP_TS_DURATION));
+ base_seqnum + i, (base_seqnum + i) * TEST_RTP_TS_DURATION));
}


/* verify we did not drop any of them */

style diverges, please run gst-indent first
ERROR: Job failed: exit code 1