[JENKINS-37140,JENKINS-36991] - Upgrade remoting to 2.61 (#2497)

Fixed issues:
* [JENKINS-37140](https://issues.jenkins-ci.org/browse/JENKINS-37140) -
JNLP Slave connection issue with *JNLP3-connect* protocol when the generated encrypted cookie contains a newline symbols.
(https://github.com/jenkinsci/remoting/pull/95)
* [JENKINS-36991](https://issues.jenkins-ci.org/browse/JENKINS-36991) -
Unable to load class when remote classloader gets interrupted.
(https://github.com/jenkinsci/remoting/pull/94)

Enhancements:
* Improve diagnostics for Jar Cache write errors.
(https://github.com/jenkinsci/remoting/pull/91)