ximagesink, xvimagesink: don't use XkbKeycodeToKeysym if Xkb is unavailable

ximagesink and xvimagesink use XkbKeycodeToKeysym when the key event is
received. However, this function returns NoSymbol if Xkb is unavailable.

This causes all key events to be translated to "unknown" key when running
ximagsink under some VNC.

Fix it by using XKeycodeToKeysym if Xkb is unavailable.
20 jobs for fix-ximagesink in 62 minutes and 27 seconds (queued for 2 seconds)
latest
Status Job ID Name Coverage
  Preparation
passed #312237
gst indent

00:00:30

passed #312236
manifest

00:00:42

 
  Build
passed #312238
build fedora x86_64

00:09:17

passed #312239
build nodebug fedora x86_64

00:09:07

 
  Test
passed #312240
check fedora

00:04:45

passed #312241
integration testsuites fedora

00:13:47

 
  Full Builds
passed #312243
build cerbero android universal

00:11:22

passed #312244
build cerbero cross win32

00:07:28

passed #312245
build cerbero cross win64

00:05:06

passed #312242
build cerbero fedora x86_64

00:06:35

 
  Full Tests
passed #312249
valgrind bad

00:04:42

passed #312246
valgrind base

00:10:10

passed #312250
valgrind ges

00:04:45

failed #312656
valgrind good

00:17:05

passed #312248
valgrind ugly

00:02:10

failed #312633
valgrind good

00:06:36

failed #312528
valgrind good

00:09:16

failed #312247
valgrind good

00:07:47

 
  Apps
skipped #312251
android universal examples
 
  Deploy
skipped #312252
documentation
 
Name Stage Failure
failed
valgrind good Full Tests
           Total: 643
Uploading artifacts...
gst-build/build/meson-logs/: found 2 matching files
validate-logs: found 1384 matching files

Uploading artifacts to coordinator... ok
id=312656 responseStatus=201 Created token=LSAEs5_x
Uploading artifacts...
validate-logs/*.xml: found 1 matching files

Uploading artifacts to coordinator... ok
id=312656 responseStatus=201 Created token=LSAEs5_x
ERROR: Job failed: exit code 1