Import grpcio 0.6.0

And add metadata files using the following command:
get_rust_pkg.py --add3prf -v grpcio-0.6.0 -o grpcio

Test: none
Change-Id: I53cc0feb5c9d24eacb62331b968cab4ec85f60a6
diff --git a/scripts/format-grpc-sys b/scripts/format-grpc-sys
new file mode 100755
index 0000000..d97445a
--- /dev/null
+++ b/scripts/format-grpc-sys
@@ -0,0 +1,2 @@
+#!/usr/bin/env bash
+clang-format-5.0 -i grpc-sys/grpc_wrap.cc