Use 2.3.1.GA -- that's the version that ships with 7.1.0. The difference is that I make sure that no older versions of resteasy are included via transitive dependencies. FWIW, this isn't my EXACT pom. The first two dependencies are in a parent pom while the last two are in a submodule, hence the lack of version tags in the last two dependencies.
I ran into the same error moving to 7.1.0, and this thread was hugely helpful in fixing it. But in my case the fix turned out to be simpler, and I thought I should share.
In my original POM, as in Ziggy's, I had a simple dependency on resteasy-jaxrs. Meaning that I was deploying that library in my WAR file. And therefore I was impacted by the internal resteasy issue that Rick explained.
But I was able fix this by simply flagging the dependency as "provided":
Meaning that I am not deploying resteasy at all. JBoss includes a valid version of the resteasy libs, so no need to bundle them with my app.
This fix might not work for everybody. There could be scenarios where you actually need to deploy resteasy. But if anybody else has this problem, I'd suggest trying the simple fix first.