For the moment, it will allow running 'make check' that does not conflict with
an already running loolwsd (eg. from 'make run'). Later we can consider
running more tests in parallel.
Put this inside #if, add the 'override' back for current Poco. Avoids
"warning: 'expectContinue' overrides a member function but is not
marked 'override'" when compiling against current Poco.
Not sure what good it would do to define it at all if compiling
against a bleeding-edge Poco as it won't call it anyway?
