Refactor buck external dependencies

Change-Id: Ia4b99493407eb7d4e893804cba6b944f758f085e
diff --git a/providers/null/BUCK b/providers/null/BUCK
index dcb01a2..440c4a8 100644
--- a/providers/null/BUCK
+++ b/providers/null/BUCK
@@ -1,5 +1,6 @@
 COMPILE_DEPS = [
     '//lib:CORE_DEPS',
+    '//lib:NETTY',
     '//lib:org.apache.karaf.shell.console',
     '//cli:onos-cli',
 ]