Do not crash if no console port is available for VBox

I don't know how user manage to fall in this situation.

Fix #127

gns3server/modules/virtualbox/virtualbox_vm.py

@@ -189,7 +189,7 @@ class VirtualBoxVM(BaseVM):
         # add a guest property to let the VM know about the GNS3 project directory
         yield from self.manager.execute("guestproperty", ["set", self._vmname, "ProjectDirInGNS3", self.working_dir])
 
-        if self._enable_remote_console:
+        if self._enable_remote_console and self._console is not None:
             self._start_remote_console()
 
     @asyncio.coroutine

tests/modules/virtualbox/test_virtualbox_manager.py

@@ -38,12 +38,14 @@ def test_vm_invalid_vboxmanage_path(manager):
         with pytest.raises(VirtualBoxError):
             manager.find_vboxmanage()
 
+
 def test_vm_non_executable_vboxmanage_path(manager):
     tmpfile = tempfile.NamedTemporaryFile()
     with patch("gns3server.config.Config.get_section_config", return_value={"vboxmanage_path": tmpfile.name}):
         with pytest.raises(VirtualBoxError):
             manager.find_vboxmanage()
 
+
 def test_vm_invalid_executable_name_vboxmanage_path(manager, tmpdir):
     path = str(tmpdir / "vpcs")
     with open(path, "w+") as f:
@@ -54,6 +56,7 @@ def test_vm_invalid_executable_name_vboxmanage_path(manager, tmpdir):
         with pytest.raises(VirtualBoxError):
             manager.find_vboxmanage()
 
+
 def test_vboxmanage_path(manager, tmpdir):
     path = str(tmpdir / "VBoxManage")
     with open(path, "w+") as f:
@@ -62,4 +65,3 @@ def test_vboxmanage_path(manager, tmpdir):
     tmpfile = tempfile.NamedTemporaryFile()
     with patch("gns3server.config.Config.get_section_config", return_value={"vboxmanage_path": path}):
         assert manager.find_vboxmanage() == path
-

tests/modules/virtualbox/test_virtualbox_vm.py

@@ -54,4 +54,3 @@ def test_vm_invalid_virtualbox_api_version(loop, project, manager):
         with pytest.raises(VirtualBoxError):
             vm = VirtualBoxVM("test", "00010203-0405-0607-0809-0a0b0c0d0e0f", project, manager, "test", False)
             loop.run_until_complete(asyncio.async(vm.create()))
-