Add an openSUSE Tumbleweed devstack non-voting check job

This adds the necessary fixes to pass a devstack run
on openSUSE Tumbleweed. Also removes opensuse 42.2 as it
is EOL for some time already and no longer actively tested
in the OpenStack infra.

Depends-On: I1b68c08c07cf6653ea58506f738cbe0054b38f3a
Change-Id: I2894482deef063fd02b0818c695a2ddbf6767039
diff --git a/functions-common b/functions-common
index df295a3..279cfcf 100644
--- a/functions-common
+++ b/functions-common
@@ -373,6 +373,9 @@
         DISTRO="f$os_RELEASE"
     elif [[ "$os_VENDOR" =~ (openSUSE) ]]; then
         DISTRO="opensuse-$os_RELEASE"
+        # Tumbleweed uses "n/a" as a codename, and the release is a datestring
+        # like 20180218, so not very useful.
+        [ "$os_CODENAME" = "n/a" ] && DISTRO="opensuse-tumbleweed"
     elif [[ "$os_VENDOR" =~ (SUSE LINUX) ]]; then
         # just use major release
         DISTRO="sle${os_RELEASE%.*}"