Update remoting to 2.60 (#2403)

Changes summary:

Fixed issues:
* [JENKINS-22722](https://issues.jenkins-ci.org/browse/JENKINS-22722) - 
Make the channel reader tolerant against Socket timeouts. 
(https://github.com/jenkinsci/remoting/pull/80)
* [JENKINS-32326](https://issues.jenkins-ci.org/browse/JENKINS-32326) - 
Support no_proxy environment variable. 
(https://github.com/jenkinsci/remoting/pull/84)
* [JENKINS-35190](https://issues.jenkins-ci.org/browse/JENKINS-35190)  - 
Do not invoke PingFailureAnalyzer for agent=>master ping failures. 
(https://github.com/jenkinsci/remoting/pull/85)
* [JENKINS-31256](https://issues.jenkins-ci.org/browse/JENKINS-31256) - 
 <code>hudson.Remoting.Engine#waitForServerToBack</code> now uses credentials for connection. 
(https://github.com/jenkinsci/remoting/pull/87)
* [JENKINS-35494](https://issues.jenkins-ci.org/browse/JENKINS-35494) - 
Fix issues in file management in <code>hudson.remoting.Launcher</code> (main executable class). 
(https://github.com/jenkinsci/remoting/pull/88)

Enhancements:
* Ensure a message is logged if remoting fails to override the default <code>ClassFilter</code>. 
(https://github.com/jenkinsci/remoting/pull/80)