Add getExportedNamespace NB callback

This callback replaces getVendorNamespace(). Fix nativeloader
to use NativeBridgeGetExportedNamespace instead of
NativeBridgeGetVendorNamespace.

Bug: http://b/121248172
Bug: http://b/121372395
Test: make
Change-Id: I8fa2081e37815f6f65490c9536bed0687b7f1e77
diff --git a/libnativeloader/native_loader.cpp b/libnativeloader/native_loader.cpp
index ad967db..47af90d 100644
--- a/libnativeloader/native_loader.cpp
+++ b/libnativeloader/native_loader.cpp
@@ -300,7 +300,7 @@
         return nullptr;
       }
 
-      native_bridge_namespace_t* vendor_ns = NativeBridgeGetVendorNamespace();
+      native_bridge_namespace_t* vendor_ns = NativeBridgeGetExportedNamespace(kVendorNamespaceName);
 
       if (!NativeBridgeLinkNamespaces(ns, nullptr, system_exposed_libraries.c_str())) {
         *error_msg = NativeBridgeGetError();