修复执行php bin/swoft stop命令时master进程异常未退出的问题，以及停止失败后，pid文件被删除的问题 (#134)

* 修复执行php bin/swoft stop命令时master进程异常未退出的问题；
修复执行php bin/swoft stop失败，但pid文件仍被删除的问题。

* Update AbstractServer.php

src/Bootstrap/Server/AbstractServer.php

@@ -127,25 +127,25 @@ public function reload($onlyTask = false)
      */
     public function stop(): bool
     {
+        //获取master进程ID
+        $masterPid = $this->serverSetting['masterPid'];
+        //使用swoole_process::kill代替posix_kill
+        $result = \swoole_process::kill($masterPid);
         $timeout = 60;
         $startTime = time();
-        $this->serverSetting['masterPid'] && posix_kill($this->serverSetting['masterPid'], SIGTERM);
-
-        $result = true;
-        while (1) {
-            $masterIslive = $this->serverSetting['masterPid'] && posix_kill($this->serverSetting['masterPid'], SIGTERM);
-            if ($masterIslive) {
-                if (time() - $startTime >= $timeout) {
-                    $result = false;
-                    break;
+        while (true) {
+            //检测进程是否退出
+            if(!\swoole_process::kill($masterPid, 0)) {
+                //判断是否超时
+                if(time() - $startTime >= $timeout) {
+                    return false;
                 }
                 usleep(10000);
                 continue;
             }
-
-            break;
+            
+            return true;
         }
-        return $result;
     }
 
     /**
@@ -159,7 +159,7 @@ public function isRunning(): bool
         $pFile = $this->serverSetting['pfile'];
 
         // Is pid file exist ?
-        if (file_exists($pFile)) {
+        if (\file_exists($pFile)) {
             // Get pid file content and parse the content
             $pidFile = file_get_contents($pFile);
             $pids = explode(',', $pidFile);