Wrong PID in opennms.pid

Steps to reproduce:

1) Start OpenNMS

2) Find the actual PID of the OpenNMS JVM via }}{{ps command:

[vagrant@horizon-24-1-2 opennms]$ ps -ef | grep 'java.*opennms.*bootstra[p]'
root      7021  7019  3 16:15 ?        00:03:59 /usr/lib/jvm/java-1.8.0-openjdk/bin/java -Djava.endorsed.dirs=/opt/opennms/lib/endorsed -Dopennms.home=/opt/opennms -Xmx1024m -XX:+HeapDumpOnOutOfMemoryError -Dcom.sun.management.jmxremote.authenticate=true -Dcom.sun.management.jmxremote.login.config=opennms -Dcom.sun.management.jmxremote.access.file=/opt/opennms/etc/jmxremote.access -DisThreadContextMapInheritable=true -Dgroovy.use.classvalue=true -XX:MaxMetaspaceSize=512m -Djava.io.tmpdir=/opt/opennms/data/tmp -XX:+StartAttachListener -jar /opt/opennms/lib/opennms_bootstrap.jar start 

3) Compare against the value in /var/log/opennms/opennms.pid:

[vagrant@horizon-24-1-2 opennms]$ cat /var/log/opennms/opennms.pid 
7019

Expected result: PID in file is same as PID in column 2 in output of (2) — 7021 in this case

Actual result: PID differs

Notes:

• The value in the PID file seems to be consistently equal to the parent PID, i.e. the PID of the OPENNMS_HOME/bin/opennms shell script
• The value in karaf.pid is the correct value that should be in opennms.pid
• I think the introduction of the runCmd function in the start / stop script (commit 24221ac2d0d92c839878209e328477fec4265c76) is the proximate cause, having changed the semantics of the "last background process"
• This bug doesn't seem to break the control script, perhaps because it uses the Attach API, but it does break tools like generate-opennms-thread-dump which read opennms.pid