CIP-1673 implement hps master shutdown and subarray obs state restart in controller off command

• refactored the CbfController OffCommand per CIP-1673
• added HPS Master shutdown to talondx component manager
• fixed unsubscribe bug in TalonBoard device
• commented out unconfigure/abort/obsreset pending CIP-1850 implementation

Tara's changes

• talon_lru_component_manager.py > off - use threads to turn off talon board device servers
• talon_board_component_manager.py > off - move updating power mode to the end of the function
• cbfcontroller_component_manager.py > off - during the final device state check, ignore serialization errors inside the poll block (still log them), to allow for retries up to the timeout specified in the poll block (follow up bug created, CIP-1899)
• talondx_component_manager.py > configuring talons - move self.proxies initialization outside of each configure_talon_thread, so as not to overwrite the field in the case of multiple talons