Remove support for opensuse

We haven't been testing the distro for a while in CI, e.g. in
Tempest, the jobs on opensuse15 haven't been executed for a year
now.
Therefore the patch removes opensuse support from devstack.

Closes-Bug: #2002900
Change-Id: I0f5e4c644e2d14d1b8bb5bc0096d1469febe5fcc
diff --git a/lib/nova b/lib/nova
index 3aa6b9e..f34e823 100644
--- a/lib/nova
+++ b/lib/nova
@@ -448,8 +448,8 @@
 
     iniset $NOVA_CONF key_manager backend nova.keymgr.conf_key_mgr.ConfKeyManager
 
-    if is_fedora || is_suse; then
-        # nova defaults to /usr/local/bin, but fedora and suse pip like to
+    if is_fedora; then
+        # nova defaults to /usr/local/bin, but fedora pip like to
         # install things in /usr/bin
         iniset $NOVA_CONF DEFAULT bindir "/usr/bin"
     fi
@@ -523,7 +523,7 @@
 
     # nova defaults to genisoimage but only mkisofs is available for 15.0+
     # rhel provides mkisofs symlink to genisoimage or xorriso appropiately
-    if is_suse || is_fedora; then
+    if is_fedora; then
         iniset $NOVA_CONF DEFAULT mkisofs_cmd /usr/bin/mkisofs
     fi