qa/distros: add single-container-host.yaml

This is a single, possibly preferred, os + container runtime
combination.

Signed-off-by: Sage Weil <sage@newdream.net>

diff --git a/qa/distros/single-container-host.yaml b/qa/distros/single-container-host.yaml
new file mode 120000 (symlink)
index 0000000..f71756d
--- /dev/null
+++ b/qa/distros/single-container-host.yaml
@@ -0,0 +1 @@
+container-hosts/centos_8.stream_container_tools_crun.yaml
\ No newline at end of file