This is regression in comparison to EAP6.
The patch for bz [1] was applied to resteasy product branch but not to the upstream master and 2.3 branch.
Therefore the Resteasy 3.0.13.Final present in EAP7.0.0.DR13 contains regression in comparisson to EAP 6.4.x.
The missing commits (present currently only in product 2.3.12.Final branch) are [2] and [3].

[1] https://bugzilla.redhat.com/show_bug.cgi?id=1233253
[2] http://git.app.eng.bos.redhat.com/git/resteasy.git/commit/?h=2.3.12.Final&id=f81a5712d46abc295cd582dbaa63c5a14d22a778
[3] http://git.app.eng.bos.redhat.com/git/resteasy.git/commit/?h=2.3.12.Final&id=05569e515db8a942d63f4eca2f2ec437515b6696