rtsp-stream: explicitly set caps on udpsrc elements

This causes them to send caps events before data flow, which is
usually a pretty correct thing to do!

Not doing so manifested in a bug where ssrcdemux wouldn't forward
the caps it had received with an extra ssrc field, as it hadn't
received any caps event.

Fixes #85

Part-of: <gstreamer/gst-rtsp-server!141>
30 jobs for !141 with udpsrc-caps in 32 minutes and 42 seconds (queued for 5 seconds)
detached
Status Job ID Name Coverage
  Build Docker
passed #3458435
alpine amd64 manifest builder docker

00:00:15

passed #3458433
android docker

00:00:15

passed #3458432
cerbero fedora amd64 docker

00:00:15

passed #3458430
fedora amd64 docker

00:03:46

passed #3458437
gst-indent amd64 docker

00:00:19

 
  Preparation
passed #3458440
gst indent

00:00:16

passed #3458438
manifest

00:00:26

 
  Build
passed #3458456
gstreamer
build cerbero cross-android universal

00:09:23

passed #3458460
gst-ios-13.2
build cerbero cross-ios universal

00:24:26

passed #3458457
gstreamer
build cerbero cross win32

00:07:17

passed #3458458
gstreamer
build cerbero cross win64

00:04:34

passed #3458455
gstreamer
build cerbero fedora x86_64

00:04:38

passed #3458459
gst-macos-10.15
build cerbero macos x86_64

00:12:32

passed #3458446
build clang fedora x86_64

00:06:32

manual #3458454
1809 windows docker allowed to fail manual
build msys2
passed #3458442
build nodebug fedora x86_64

00:06:10

passed #3458443
build static fedora x86_64

00:05:02

passed #3458445
build static nodebug fedora x86_64

00:05:32

passed #3458897
1809 windows docker
build vs2017 amd64

00:16:07

passed #3458900
1809 windows docker
build vs2017 x86

00:16:22

failed #3458448
1809 windows docker
build vs2017 amd64

00:10:13

failed #3458450
1809 windows docker
build vs2017 x86

00:10:16

 
  Test
passed #3458461
gstreamer
check fedora

00:04:31

passed #3458462
gstreamer
integration testsuites fedora 1/4

00:14:49

passed #3458463
gstreamer
integration testsuites fedora 2/4

00:13:28

passed #3458464
gstreamer
integration testsuites fedora 3/4

00:11:51

passed #3458465
gstreamer
integration testsuites fedora 4/4

00:12:52

 
  Integrate
passed #3458466
cross-android universal examples

00:06:25

passed #3458468
gst-ios-13.2
cross-ios universal examples

00:01:28

passed #3458467
documentation

00:09:51