Acceptance criteria 1:
rc_parallel_start="YES" causes /etc/rc to pass '-p' option to rcorder in the early and late passes. An rc_parallel_start that is undefined, "NO" or any value other than "YES", "TRUE", "ON", or "1" (using checkyesno) will cause /etc/rc to omit the '-p' option to rcorder.
Acceptance criteria 2:
If rcorder returns multiple script paths per line separated by a space, /etc/rc will execute each script - with each script path passed to run_rc_script - as a background task. This behavior is independent of the rc_parallel_start option.
Acceptance criteria 3:
After processing each line of output from rcorder, /etc/rc will pause by calling 'wait' to allow all rc script tasks to complete before proceeding to the next line of output from rcorder. This behavior is independent of the rc_parallel_start option.
Acceptance criteria 4:
In the presence of the "old" rcorder (-p not supported), this /etc/rc script still functions correctly but without parallel execution.
Note: in the future, parallel start-up may become the default. This does not eliminate the need for the rc_parallel_start variable. Supporting rc_parallel_start="NO" in /etc/rc.conf remains useful for debugging rc scripts.