template: don't return empty list on exit value fail (#20)

Addresses issue of re-downloading of templates when listvmtmplt.sh script fails (non 0 exit code) or timesout

Author: Pearl1594

services/secondary-storage/server/src/org/apache/cloudstack/storage/template/DownloadManagerImpl.java

@@ -805,6 +805,10 @@ private List<String> listVolumes(String rootdir) {
         script.add("-r", rootdir);
         ZfsPathParser zpp = new ZfsPathParser(rootdir);
         script.execute(zpp);
+        if (script.getExitValue() != 0) {
+            s_logger.error("Error while executing script " + script.toString());
+            throw new CloudRuntimeException("Error while executing script " + script.toString());
+        }
         result.addAll(zpp.getPaths());
         s_logger.info("found " + zpp.getPaths().size() + " volumes" + zpp.getPaths());
         return result;
@@ -817,6 +821,10 @@ private List<String> listTemplates(String rootdir) {
         script.add("-r", rootdir);
         ZfsPathParser zpp = new ZfsPathParser(rootdir);
         script.execute(zpp);
+        if (script.getExitValue() != 0) {
+            s_logger.error("Error while executing script " + script.toString());
+            throw new CloudRuntimeException("Error while executing script " + script.toString());
+        }
         result.addAll(zpp.getPaths());
         s_logger.info("found " + zpp.getPaths().size() + " templates" + zpp.getPaths());
         return result;