BUGFIX: Fix RequestHandlerTest outputting headers
BUGFIX: Fix RequestHandlerTest outputting headers

This is the fix for 6.0 to 6.2 - 6.3 and up have a different
sendResponse() implementation (for which the fix exists in master and
has been backported to 5.3, where it is completely unused.)

neos/flow,neos/flow,neos/flow,neos/flow