Added BSW_EFSSecondary test group for EFS lab secondary servers (bos-02, syd-05).
EFS secondary servers share a depot volume with their primary (bos-02 shares with
bos-01; syd-05 shares with syd-04). BSW_OtherHosts runs DANGER_CLEAN which wipes
all SDP mount points including the shared EFS depot, destroying the seed checkpoint.
BSW_EFSSecondary skips DANGER_CLEAN and uses install_sdp.sh -ued (use existing data)
to refresh SDP scripts/binaries while preserving the EFS-shared depot content.
Note: lab_engine handles removal of any stray license files on edge/downstream
servers after checkpoint replay (per BSW-43 fix).