OVN : include source compliation functions

This patch moves the OVS compilation module from Neutron into DevStack.
It also renamed it to "ovs_source" to highlight its function, and the
include has been moved to where the rest of the includes are located.

Although this module is not required since by default DevStack installs
OVS/OVN from the host OS packages instead of compiling from source,
this is a nice to have as it avoids having bits and pieces of the code
scattered around multiple repositories.

Co-Authored-By: Lucas Alvares Gomes <lucasagomes@gmail.com>
Change-Id: I39ec9ce0a91bea05cf8c446a9767ab879ac8e8f3
diff --git a/lib/neutron_plugins/ovn_agent b/lib/neutron_plugins/ovn_agent
index 4af1340..71a4c60 100644
--- a/lib/neutron_plugins/ovn_agent
+++ b/lib/neutron_plugins/ovn_agent
@@ -21,6 +21,9 @@
 source ${TOP_DIR}/lib/neutron_plugins/ovs_base
 source ${TOP_DIR}/lib/neutron_plugins/openvswitch_agent
 
+# Load devstack ovs compliation and loading functions
+source ${TOP_DIR}/lib/neutron_plugins/ovs_source
+
 # Defaults
 # --------
 
@@ -395,9 +398,6 @@
     sudo ln -s $OVS_RUNDIR $OVN_RUNDIR
 
     if [[ "$OVN_BUILD_FROM_SOURCE" == "True" ]]; then
-        # Load devstack ovs base functions
-        source $NEUTRON_DIR/devstack/lib/ovs
-
         # If OVS is already installed, remove it, because we're about to
         # re-install it from source.
         for package in openvswitch openvswitch-switch openvswitch-common; do