[umpire] Add RPC base class for CLI and DUT

Umpire daemon provides remote procedure calls to command line utility
and device under test. This change provides the base class UmpireRPC
and the RPC function decorator @RPCCall.

BUG=chrome-os-partner:28282
TEST=None

Change-Id: Ia62e395d9db61bcd0e4818cefa0c27dcc127b7bc
Reviewed-on: https://chromium-review.googlesource.com/198978
Commit-Queue: Rong Chang <rongchang@chromium.org>
Tested-by: Rong Chang <rongchang@chromium.org>
Reviewed-by: Rong Chang <rongchang@chromium.org>
1 file changed