fix: when use SGLANG_PORT this env,port is str (#4528)

Signed-off-by: rongfu.leng <lenronfu@gmail.com>

python/sglang/srt/utils.py

@@ -1602,6 +1602,7 @@ def get_ip() -> str:
 def get_open_port() -> int:
     port = os.getenv("SGLANG_PORT")
     if port is not None:
+        port = int(port)
         while True:
             try:
                 with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s: