Using the new credentials API allows using generic APIs instead of
Netty-specific ones and allows using grpc-netty-shaded. The new API is
still marked experimental, but it is intended to be stabilized which
isn't the case for the Netty-specific API.
The client now looks more similar to HelloWorldClient.
* examples: use test certs for running example-tls
* fixed a typo
* update usage printout for trustCertCollectionFilePath is not optional
* Revert "update usage printout for trustCertCollectionFilePath is not optional"
This reverts commit 2dd6d87f64.
* put back the usage of using system default CA and put notes for it
* fixed cmd-line argument options
Eric Anderson
ZHANG Dapeng
Chengyuan Zhang