os/xdmcp: Don't create a new socket in XdmcpReset()

xdmcpSocket survives during the reset, there is no
need to create a new one.

This commit restores logic that was broken by
49c0f2413d in Xorg 1.19.

Signed-off-by: Alexander Volkov <a.volkov@rusbitech.ru>
(cherry picked from commit 32677ce03d793a1f2aa8871112eb3d19b3cb762f)

os/xdmcp.c

@@ -569,10 +569,9 @@ XdmcpRegisterDisplayClass(const char *name, int length)
 }
 
 static void
-xdmcp_start(void)
+xdmcp_reset(void)
 {
     timeOutRtx = 0;
-    get_xdmcp_sock();
     if (xdmcpSocket >= 0)
         SetNotifyFd(xdmcpSocket, XdmcpSocketNotify, X_NOTIFY_READ, NULL);
 #if defined(IPv6) && defined(AF_INET6)
@@ -583,6 +582,13 @@ xdmcp_start(void)
     send_packet();
 }
 
+static void
+xdmcp_start(void)
+{
+    get_xdmcp_sock();
+    xdmcp_reset();
+}
+
 /*
  * initialize XDMCP; create the socket, compute the display
  * number, set up the state machine
@@ -611,7 +617,7 @@ XdmcpReset(void)
 {
     state = XDM_INIT_STATE;
     if (state != XDM_OFF)
-        xdmcp_start();
+        xdmcp_reset();
 }
 
 /*