fix graceful restart and add unit test

tests/test_graceful_restart.sh

@@ -0,0 +1,63 @@
+#!/bin/bash
+
+PYTHON="coverage run -p -a"
+URL=http://127.0.0.1/file
+
+
+# setup processes
+$PYTHON shadowsocks/local.py -c tests/graceful.json &
+LOCAL=$!
+
+$PYTHON shadowsocks/server.py -c tests/graceful.json --forbidden-ip "" &
+SERVER=$!
+
+python tests/graceful_server.py &
+GSERVER=$!
+
+sleep 1
+
+python tests/graceful_cli.py &
+GCLI=$!
+
+sleep 1
+
+# graceful restart server: send SIGQUIT to old process and start a new one
+kill -s SIGQUIT $SERVER
+$PYTHON shadowsocks/server.py -c tests/graceful.json --forbidden-ip "" &
+NEWSERVER=$!
+
+sleep 1
+
+# check old server
+ps x | grep -v grep | grep $SERVER
+OLD_SERVER_RUNNING1=$?
+# old server should not quit at this moment
+echo old server running: $OLD_SERVER_RUNNING1
+
+sleep 1
+
+# close connections on old server
+kill -s SIGINT $GCLI
+kill -s SIGKILL $GSERVER
+kill -s SIGINT $LOCAL
+
+sleep 11
+
+# check old server
+ps x | grep -v grep | grep $SERVER
+OLD_SERVER_RUNNING2=$?
+# old server should quit at this moment
+echo old server running: $OLD_SERVER_RUNNING2
+
+# new server is expected running
+kill -s SIGINT $NEWSERVER || exit 1
+
+if [ $OLD_SERVER_RUNNING1 -ne 0 ]; then
+    exit 1
+fi
+
+if [ $OLD_SERVER_RUNNING2 -ne 1 ]; then
+    kill -s SIGINT $SERVER
+    sleep 1
+    exit 1
+fi