shell/caucase.sh: Fail sooner when caucased exits on start.

shell/caucase.sh

@@ -1232,6 +1232,13 @@ EOF
       _curlInsecure "http://$netloc" > /dev/null
       status=$?
       test $status -eq 0 && break
+      # is caucased still alive ?
+      if kill -0 "$caucased_pid" 2> /dev/null; then
+        :
+      else
+        echo "caucased exited"
+        return 1
+      fi
       # curl status 7 means "could not connect"
       if [ $status -ne 7 ]; then
         echo "curl failed while accessing test caucased with status $status"