Fix video restarting sync issue

There is a video start/stop sync issue inbetween ikvm server and
ikvm manager because newClient and clientGone callbacks are called
by a different thread from libvncserver. To fix this issue, this
commit moves the video.start() call from server to manager to
unify video control thread.

Tested:
  Open KVM web page and reload the web page by pressing F5.
  KVM page should be reloaded correctly.

Change-Id: Ic0d14ea712510318e9e8f45615a95e82aeaaddf1
Signed-off-by: Jae Hyun Yoo <jae.hyun.yoo@linux.intel.com>
diff --git a/ikvm_server.cpp b/ikvm_server.cpp
index 37a927b..35310da 100644
--- a/ikvm_server.cpp
+++ b/ikvm_server.cpp
@@ -154,6 +154,7 @@
     Server* server = (Server*)cl->screen->screenData;
 
     delete (ClientData*)cl->clientData;
+    cl->clientData = nullptr;
 
     if (server->numClients-- == 1)
     {
@@ -173,7 +174,6 @@
     {
         server->pendingResize = false;
         server->frameCounter = 0;
-        server->video.start();
     }
 
     return RFB_CLIENT_ACCEPT;