support autobuild release for installer

From: Michael Prokop <mprokop@sipwise.com>

deployment.sh

@@ -845,8 +845,8 @@ if "$NGCP_INSTALLER" ; then
     INSTALLER_PATH="http://deb.sipwise.com/spce/$INSTALLER_PATH"
   fi
 
-  # ngcp-installer from trunk
-  if [ "$INSTALLER_VERSION" = "trunk" ] || $TRUNK_VERSION ; then
+  # ngcp-installer from trunk or a release build
+  if [ "$INSTALLER_VERSION" = "trunk" ] || $TRUNK_VERSION || [ -n "$AUTOBUILD_RELEASE" ] ; then
     INSTALLER_PATH='http://deb.sipwise.com/autobuild/debian/pool/main/n/ngcp-installer/'
 
     wget --directory-prefix=debs --no-directories -r --no-parent "$INSTALLER_PATH"