[OVN] Use OVN from packages

This patch changes the OVN module from DevStack to allow for using the
OSapackaged version of OVN instead of compiling it from source.

A new variable called OVN_BUILD_FROM_SOURCE has been introduced and when
set to False (the default value) OVN will then use the packaged version
for setting up DevStack.

Note, in the stop_ovn() function, the OVN metadata agent service name
was wrong and the service wasn't being stopped as part of ./unstack.sh.
This patch also fixed it as well.

Change-Id: Ib41e3b486550200572afd6b3ba783d7644d70d44
Signed-off-by: Lucas Alvares Gomes <lucasagomes@gmail.com>
Co-Authored-By: Slawek Kaplonski <skaplons@redhat.com>
diff --git a/tools/fixup_stuff.sh b/tools/fixup_stuff.sh
index cd7ee59..25f7268 100755
--- a/tools/fixup_stuff.sh
+++ b/tools/fixup_stuff.sh
@@ -184,6 +184,14 @@
     sudo zypper up -y p11-kit ca-certificates-mozilla
 }
 
+function fixup_ovn_centos {
+    if [[ $os_VENDOR != "CentOS" ]]; then
+        return
+    fi
+    # OVN packages are part of this release for CentOS
+    yum_install centos-release-openstack-victoria
+}
+
 function fixup_all {
     fixup_keystone
     fixup_ubuntu