Re-reading the JIRA issue, it looks like the code changes were in response to Tim Fox's concerns about Remoting's shutdown behavior, but the problem itself was solved by configuration: "After increasing the client pool size I'm not getting these exceptions any more."
As for whether the code changes are included in Remoting release 2.2.3.SP1, the answer is "no." Remoting 2 has two branches that contribute releases to currently supported versions of the Enterprise Application Platform (EAP). Branch 2.2 (http://svn.jboss.org/repos/jbossremoting/remoting2/branches/2.2) contributes releases 2.2.x to EAP 4.2/4.3, and branch 2.x (https://svn.jboss.org/repos/jbossremoting/remoting2/branches/2.x) contributes release 2.4/2.5 to EAP 5.x. These code bases diverged years ago, and, though I often apply a particular fix to both branches, they are distinct. In particular, the changes referred to in JBREM-821 were made to branch 2.x, but do not exist on branch 2.2.
By the way, if you look at the "Subversion Commits" tab on JBREM-821, you'll see that all of the commits were to branch 2.x.