Add "product_available" to product available modules

"vendor_available" modules were available to product modules.
However, not all "vendor_available" modules are required to be
available to product modules. Some modules want to be available only
to product modules but not vendor modules.

To cover the requirement, we separate "product_available" from
"vendor_available".
"vendor_available" will not provide product available module.

Bug: 150902910
Test: build
Change-Id: I5c2dce7f1cac4a1af4e01022bab318ffd7aeae54
diff --git a/Android.bp b/Android.bp
index f452cf3..834ef6f 100644
--- a/Android.bp
+++ b/Android.bp
@@ -34,6 +34,7 @@
     name: "libjsoncpp",
     defaults: ["libjsoncpp_defaults"],
     vendor_available: true,
+    product_available: true,
     vndk: {
         enabled: true,
         support_system_process: true,