qa/distros/supported-random-distro$: keep support for bionic

we still want to keep supporting 18.04 LTS for octopus, don't want to
use it for cephadm, since podman dropped support for bionic.

this is octopus only commit, since it's octopus specific support and we
dropped bionic in master.

Signed-off-by: Deepika Upadhyay <dupadhya@redhat.com>

diff --git a/qa/distros/supported-random-distro$/ubuntu_18.04.yaml b/qa/distros/supported-random-distro$/ubuntu_18.04.yaml
new file mode 120000 (symlink)
index 0000000..64a66d9
--- /dev/null
+++ b/qa/distros/supported-random-distro$/ubuntu_18.04.yaml
@@ -0,0 +1 @@
+../all/ubuntu_18.04.yaml
\ No newline at end of file