fix no config panic & wingmate.yaml doc

docker/alpine/etc/wingmate/wingmate.yaml

@@ -0,0 +1,59 @@
+service:
+#  one:
+#    command: [ "wmstarter" ]
+#    environ: [ "DUMMY_PATH=/workspace/wingmate/cmd/experiment/dummy/dummy" ]
+
+  spawner:
+    command: [ "wmspawner" ]
+    user: "1200"
+
+  bgtest:
+    command:
+      - "wmstarter"
+      - "--no-wait"
+      - "--"
+      - "wmexec"
+      - "--setsid"
+      - "--"
+      - "wmbg"
+      - "--name"
+      - "test-run"
+      - "--pause"
+      - "10"
+      - "--log-path"
+      - "/var/log/wmbg.log"
+      - "--pid-file"
+      - "/var/run/wmbg.pid"
+    pidfile: "/var/run/wmbg.pid"
+
+cron:
+  cron1:
+    command:
+      - "wmoneshot"
+      - "--"
+      - "sleep"
+      - "5"
+    schedule: "*/5 * * * *"
+    environ:
+      - "WINGMATE_LOG=/var/log/cron1.log"
+      - "WINGMATE_LOG_MESSAGE=cron executed in minute 5,10,15,20,25,30,35,40,45,50,55"
+  cron2:
+    command:
+      - "wmoneshot"
+      - "--"
+      - "sleep"
+      - "5"
+    schedule: "17,42 */2 * * *"
+    environ:
+      - "WINGMATE_LOG=/var/log/cron2.log"
+      - "WINGMATE_LOG_MESSAGE=cron scheduled using 17,42 */2 * * *"
+  cron3:
+    command:
+      - "wmoneshot"
+      - "--"
+      - "sleep"
+      - "5"
+    schedule: "7,19,23,47 22 * * *"
+    environ:
+      - "WINGMATE_LOG=/var/log/cron3.log"
+      - "WINGMATE_LOG_MESSAGE=cron scheduled using 7,19,23,47 22 * * *"