Fixes two critical bugs in refresh_smart_cache() that prevented SMART
temperature collection from working:
1. Invalid smartctl parameter: Changed -n standby,after to -n standby
The 'after' parameter is not valid in smartctl 7.4 and causes:
"INVALID ARGUMENT TO -n: standby,after"
Valid syntax is standby[,STATUS[,STATUS2]] where STATUS must be numeric.
2. Broken process detection: Replaced exec -a with lock file approach
The original exec -a pulse-sensor-wrapper-refresh bash line replaced
the subshell with a new bash process that had no script to run, causing
the function to exit immediately without collecting any SMART data.
New approach uses a lock file ($CACHE_DIR/smart-refresh.lock) with
trap-based cleanup to prevent concurrent refresh operations.
Credits to @ZaDarkSide for identifying these issues in PR #672.
rcourtman
334b8c727f