Convert to openSUSE Leap 15.0 platform testing

Leap 15.0 has been released May 25th, 2018 (see
https://en.opensuse.org/Portal:15.0 ) and we'd like to
transition devstack against it and remove Leap 42.3 from
the testing matrix. Leap 15.0 is newer than Leap 42.3 as
the numbering schema of openSUSE was changed.

Co-Authored-By: Antonio Ojea <itsuugo@gmail.com>

Change-Id: I078f9a2580160c564c33e575008516f5e92239d6
diff --git a/stack.sh b/stack.sh
index 56e00bf..be3c4be 100755
--- a/stack.sh
+++ b/stack.sh
@@ -221,7 +221,7 @@
 
 # Warn users who aren't on an explicitly supported distro, but allow them to
 # override check and attempt installation with ``FORCE=yes ./stack``
-if [[ ! ${DISTRO} =~ (xenial|artful|bionic|stretch|jessie|f27|f28|opensuse-42.3|opensuse-tumbleweed|rhel7) ]]; then
+if [[ ! ${DISTRO} =~ (xenial|artful|bionic|stretch|jessie|f27|f28|opensuse-42.3|opensuse-15.0|opensuse-tumbleweed|rhel7) ]]; then
     echo "WARNING: this script has not been tested on $DISTRO"
     if [[ "$FORCE" != "yes" ]]; then
         die $LINENO "If you wish to run this script anyway run with FORCE=yes"
@@ -1137,6 +1137,7 @@
     echo_summary "Configuring Neutron"
 
     configure_neutron
+
     # Run init_neutron only on the node hosting the Neutron API server
     if is_service_enabled $DATABASE_BACKENDS && is_service_enabled neutron; then
         init_neutron