Duplicate room list in Outlook 2010 / 2013

To solve this case remove RoomFinderRecentRoomList key under HKCU:

reg delete "HKCU\Software\Microsoft\Office\15.0\Outlook\Preferences" /v RoomFinderRecentRoomList /f > nul 2>&1
reg delete "HKCU\Software\Microsoft\Office\14.0\Outlook\Preferences" /v RoomFinderRecentRoomList /f > nul 2>&1