Minio server was preventing itself to start when any notification
target is down and not running. The PR changes the behavior by
avoiding startup abort in that case, so the user will still
be able to access Minio server using mc admin commands after
a restart or set config commands.
Added support for new RPC support using HTTP POST. RPC's
arguments and reply are Gob encoded and sent as HTTP
request/response body.
This patch also removes Go RPC based implementation.