Fix for Netty wiring issue after 4.0 bump.

- After updating Netty 4.0 version,
  we sometimes see java.lang.NoClassDefFoundError: io/netty/util/internal/TypeParameterMatcher
  with backtrace insisting there's some dynamic class resolution inside Netty.

  It might be side-effect of recent native-epoll support inside karaf?
   https://github.com/netty/netty/issues/5119

- Add DynamicImport-Package for io.netty to allow deferred wiring
  http://felix.apache.org/documentation/tutorials-examples-and-presentations/apache-felix-osgi-faq.html#how-to-provide-optional-services
- Add a way to pass DynamicImport-Package on BUCK build

Change-Id: I50ec3400e940c56fb52563d84659ebb30c302235
diff --git a/bucklets/onos.bucklet b/bucklets/onos.bucklet
index ecdb88c..e5e4b0a 100644
--- a/bucklets/onos.bucklet
+++ b/bucklets/onos.bucklet
@@ -103,6 +103,7 @@
     description = '',
     debug = False,
     import_packages = '*',
+    dynamicimport_packages = '',
     export_packages = '*',
     package_name_root = 'org.onosproject',
     include_resources = NONE,
@@ -169,6 +170,7 @@
            "'%s'" % export_packages,          #packages to export
            include_resources,                 #custom includes to classpath
            web_context,                       #web context (REST API only)
+           "'%s'" % dynamicimport_packages,   #DynamicImport-Package
            description,                       #description
           )