gl/wayland: fix wayland event source burning CPU

Commit c71dd72b "gl/wayland: fix glib mainloop integration" was overeager
in removing the poll result test from the check function. This caused
dispatch to be called even if no new events are available on the
Wayland connection, which in turn would wake up the glib mainloop,
causing effectively a tight loop without ever blocking on the poll.

Fixes #603
24 jobs for gl-wayland-fix-wayland-event-source-burning-CPU in 53 minutes and 54 seconds (queued for 39 seconds)
Status Job ID Name Coverage
  Preparation
passed #449082
gst indent

00:00:39

passed #449081
manifest

00:00:48

 
  Build
passed #449088
build cerbero android universal

00:11:39

passed #449089
build cerbero cross win32

00:10:37

passed #449090
build cerbero cross win64

00:05:48

passed #449087
build cerbero fedora x86_64

00:06:58

manual #449092
gst-ios-12.2 allowed to fail manual
build cerbero ios universal
passed #449091
gst-macos-10.14
build cerbero macos x86_64

00:06:51

passed #449083
build fedora x86_64

00:06:51

passed #449084
build nodebug fedora x86_64

00:05:32

passed #449085
build static fedora x86_64

00:13:23

passed #449086
build static nodebug fedora x86_64

00:09:36

 
  Test
passed #449093
check fedora

00:05:49

passed #449094
integration testsuites fedora

00:15:02

passed #449098
valgrind bad

00:05:27

passed #449095
valgrind base

00:10:19

passed #449099
valgrind ges

00:07:29

passed #449239
valgrind good

00:11:28

passed #449097
valgrind ugly

00:03:13

failed #449224
valgrind good

00:15:17

passed #449223
valgrind good

00:09:25

failed #449096
valgrind good

00:22:48

 
  Integrate
passed #449100
android universal examples

00:07:37

passed #449101
documentation

00:04:36