[6.6][ML] do not exit the worker after warning about failed cleanup (#357)

fix a race condition if a forecast job requires overflowing to disk but cleanup of temporary storage fails.
This can cause the autodetect process to hang on exit, if more forecast requests are in the queue

relates to #350

Author: Hendrik Muhs

docs/CHANGELOG.asciidoc

@@ -44,6 +44,13 @@ Fix cause of "Sample out of bounds" error message (See {ml-pull}355[355].}
 
 === Regressions
 
+ == {es} version 6.5.5
+
+=== Bug Fixes
+Fix a race condition if a forecast job requires overflowing to disk but cleanup of temporary
+storage fails. This can cause the autodetect process to hang on exit, if more forecast requests
+are in the queue. (See {ml-pull}352[352].)
+
  == {es} version 6.5.3
 
 === Bug Fixes

lib/api/CForecastRunner.cc

@@ -222,7 +222,6 @@ void CForecastRunner::forecastWorker() {
                     LOG_WARN(<< "Failed to cleanup temporary data from: "
                              << forecastJob.s_TemporaryFolder << " error "
                              << errorCode.message());
-                    return;
                 }
             }
         }