Test gst_rtspserver.test_shared_udp seems to be flaky

It timed out in one of my (unrelated) CI pipelines: https://gitlab.freedesktop.org/philn/gst-plugins-bad/-/jobs/95513

Failed to acquire bus: No such file or directory
No journal files were found.
No coredumps found.
check.gst-rtsp-server.gst_rtspserver.test_shared_udp: Timeout 'Application timed out: 120.0 secs'
       You can reproduce with: GST_PLUGIN_PATH_1_0='/builds/philn/gst-plugins-bad/gst-build/build' GST_REGISTRY='/builds/philn/gst-plugins-bad/gst-build/build/subprojects/gst-rtsp-server/tests/check/gst/rtspserver.registry' GST_STATE_IGNORE_ELEMENTS='' GST_CHECKS='test_shared_udp' CK_DEFAULT_TIMEOUT='120' GST_PLUGIN_LOADING_WHITELIST='gstreamer:gst-plugins-base:gst-plugins-good:gst-plugins-bad:gst-rtsp-server' GST_PLUGIN_SYSTEM_PATH_1_0='' /builds/philn/gst-plugins-bad/gst-build/build/subprojects/gst-rtsp-server/tests/check/gst_rtspserver

Dumping log files on failure

Dumping contents of /builds/philn/gst-plugins-bad/validate-output/logs/check/gst-rtsp-server/gst_rtspserver/test_shared_udp

=================
Test name: check.gst-rtsp-server.gst_rtspserver.test_shared_udp
Command: '/builds/philn/gst-plugins-bad/gst-build/build/subprojects/gst-rtsp-server/tests/check/gst_rtspserver'
=================

Running suite(s): rtspserver
0%: Checks: 1, Failures: 0, Errors: 1
../subprojects/gst-rtsp-server/tests/check/gst/rtspserver.c:385:E:general:test_shared_udp:0: (after this point) Test timeout expired
Check suite rtspserver ran in 120.028s (tests failed: 1)