[pvr] don't save channel settings every time an audio/video setting
is changed
[pvr] remove CPVRChannelSettingsSaveJob since it is now unused
[pvr] implement Save/LoadCurrentChannelSettings() directly in PVRManager
instead of passing the call along to PVRClients. Also call the methods
in the appropriate places (OpenLiveStream, CloseLiveStream and
PerformChannelSwitch)
[pvr] remove m_bIsValidChannelSettings from PVRClients since it is unused
[cosmetics] removed "Current" from the save/load method names and made
them private
[pvr] always persist channel settings, they defaults check always returns true
anyway