* Fix TCP tests to use OS-selected port
https://build.spring.io/browse/INTSAMPLES-NIGHTLY-2413
Modify all the `tcpclientserver` tests to rely on the OS-selected port,
in other words set `0` to the server port and get the real port for the
client when server is listening
* * Upgrade to Gradle-4.6
* Fix Travis config do not perform assemble task