Track priv_app firstboot_prop denial

This denial should not be allowed. Add bug information to the denial
to give context.

Bug: 63801215
Test: build
Change-Id: I3dc5ce6a5aa1c6bf74c6fd13cab082c7f263c4e8
diff --git a/private/bug_map b/private/bug_map
new file mode 100644
index 0000000..8f28a66
--- /dev/null
+++ b/private/bug_map
@@ -0,0 +1 @@
+priv_app firstboot_prop file 63801215