Unified ISSU: LFM

The LFM protocol supports unified ISSU with some restrictions. Connectivity failures that occur during the unified ISSU period will not be detected until after unified ISSU has completed. If unified ISSU is initiated while discovery is in progress, the discovery will complete only after unified ISSU has finished. LFM features that require Routing Engine involvement will not work during the unified ISSU period. Unified ISSU cannot run on the local and remote ends at the same time.