Add vndservicemanager.

vndservicemanager is the context manager for
binder services that are exclusively used from
the vendor binder domain, "/dev/vndbinder";
these services can only be registered and accessed
by vendor processes.

To facilitate code re-use, vndservicemanager
is just framework servicemanager accessing the
vendor binder devnode.

Bug: 36052864
Test: modified binder_test to use /dev/vndbinder

Change-Id: Iac19a1180321a5be78d7be5ceb4ba211c593dc47