Enhanced sdp_sync.sh to allow per-machine configurable setting of the
SDP_STATUS_DIRS setting. So of helix-01 has /p4/1/bin/ and /p4/abc/bin,
and helix-02 has /p4/acme/bin and /p4/fgs/bin, that can be configured
using optional per-host config file named sdp_status_dirs.<host>.cfg
in /p4/common/config.