Ping others can be confusing

[zhouaihui]

#118 did a good job. But something can be improved.

Using send instead of _grpc_ping can result in cleaner code, but it may not be good enough for users.

When parties cannot initiate the code simultaneously, numerous error logs may appear during initialization, which can be confusing for users.

Additionally, the _grpc_ping function disregards exceptions and sets error messages to debug, which may lead users to assume that failed pings are normal. Can this be improved in send?