EpgContainer: Fix Deadlock when calling Observer with lock
[EPG] Do *Persist*() calls on a copy of m_epgs

We can get in a situation where PersistAll() and PersistTables() are
running simutaneously, leading to memory corruption.
[EPG] Make sure we catch requests to update during update.
[EPG] Fixes deadlock enteringing livetv during EPG update