GROOVY-6456: AbstractHttpServlet.applyResourceNameMatcher race condition

converted Patch supplied by Andrej Fink to pull request
GROOVY-6456: AbstractHttpServlet.applyResourceNameMatcher race condition

updated Patch submitted by Andrej Fink
Merge pull request #294 from PascalSchumacher/GROOVY-6456

GROOVY-6456: AbstractHttpServlet.applyResourceNameMatcher race condition