Improve vmrun timeout message

Ref https://github.com/GNS3/gns3-gui/issues/1967

gns3server/compute/vmware/__init__.py

@@ -396,7 +396,7 @@ class VMware(BaseManager):
         try:
             stdout_data, _ = yield from asyncio.wait_for(process.communicate(), timeout=timeout)
         except asyncio.TimeoutError:
-            raise VMwareError("vmrun has timed out after {} seconds!\nTry to run {} in a terminal to see more informations.\nAnd make sure GNS3 and VMware run under the same user.".format(timeout, command_string))
+            raise VMwareError("vmrun has timed out after {} seconds!\nTry to run {} in a terminal to see more informations.\n\nMake sure GNS3 and VMware run under the same user and whitelist vmrun.exe in your antivirus.".format(timeout, command_string))
 
         if process.returncode:
             # vmrun print errors on stdout