Remove LBaaS support from devstack

Devstack support for LBaaS is being migrated to an external
plugin in the neutron-lbaas repository.  The only LBaaS-
specific code that remains in devstack is a hook to support
existing configs that enable q-lbaas.  In that case, load
the external plugin if necessary.

Change-Id: I592f64407ccf1e722b8d9788917879d0236acf0b
Depends-On: I64a94aeeabe6357b5ea7796e34c9306c55c9ae67
diff --git a/functions-common b/functions-common
index df69cba..267dfe8 100644
--- a/functions-common
+++ b/functions-common
@@ -1601,6 +1601,25 @@
     GITBRANCH[$name]=$branch
 }
 
+# is_plugin_enabled
+#
+# Has a particular plugin been enabled?
+function is_plugin_enabled {
+    local plugins=$@
+    local plugin
+    local enabled=1
+
+    # short circuit if nothing to do
+    if [[ -z ${DEVSTACK_PLUGINS} ]]; then
+        return $enabled
+    fi
+
+    for plugin in ${plugins}; do
+        [[ ,${DEVSTACK_PLUGINS}, =~ ,${plugin}, ]] && enabled=0
+    done
+    return $enabled
+}
+
 # fetch_plugins
 #
 # clones all plugins