mgmt: InternalFace processes Interest asynchronously

This avoids forwarding's incoming Data pipeline to be called
within incoming Interest pipeline - this property holds for
other faces, and is expected by forwarding.

refs #1419

Change-Id: I3eb1ca84830d5d8aefe0ae67a562acdd835ca5ca
diff --git a/tests/mgmt/fib-manager.cpp b/tests/mgmt/fib-manager.cpp
index 5076e0d..d672ab7 100644
--- a/tests/mgmt/fib-manager.cpp
+++ b/tests/mgmt/fib-manager.cpp
@@ -228,6 +228,7 @@
          command.getName(), 400, "Malformed command");
 
   face->sendInterest(command);
+  g_io.run_one();
 
   BOOST_REQUIRE(didCallbackFire());
 }