HA: FPC self-healing

Supported platforms allow you to configure Packet Forwarding Engine-related error levels (fatal, major, or minor) and the actions to perform (alarm, disable-pfe, or log) when a specified threshold is reached. Previously, Packet Forwarding Engine-related errors would disable the FPC. Using this command Packet Forwarding Engine errors can be isolated thereby reducing the need for a field replacement. This command is available at the [edit chassis fpc slot-number] and [edit chassis] hierarchy levels.