cogl/tests: Use less verbose run-tests.sh on single tests run by meson

Use less verbose output when run-tests.sh is running only a test and we're
requested for less verbose output.

GNOME/mutter!442
3 jobs for !442 with meson-test-suites in 3 minutes and 34 seconds (queued for 1 second)
detached
Status Job ID Name Coverage
  Review
passed #263832
check-commit-log

00:00:36

 
  Build
passed #263833
build-mutter

00:02:30

 
  Test
failed #263834
test-mutter

00:00:27

 
Name Stage Failure
failed
test-mutter Test
Using Docker executor with image registry.gitlab.gnome.org/gnome/mutter/master:v1 ...
Pulling docker image registry.gitlab.gnome.org/gnome/mutter/master:v1 ...
Using docker image sha256:a5649ee64ed0e8c3a1292c95752c92cd9a193f58adf29dab49f4f07f178f3f9f for registry.gitlab.gnome.org/gnome/mutter/master:v1 ...
Running on runner-f23948e6-project-574-concurrent-0 via progress.gnome.org...
Cloning repository...
Cloning into '/builds/3v1n0/mutter'...
Checking out af269b2f as meson-test-suites...
fatal: reference is not a tree: af269b2fb96d81be3752b224eeae76c41a2cbd34
ERROR: Job failed: exit code 1