We are currently using the background_fetch plugin with ATS 5.3.2 per remap. We configure the background_fetch plugin in remap.config using the relative path to a config file in etc/trafficserver. While testing ATS 6.2.1 with our configs, I found that the background_fetch plugin no-longer looks for config files relative to the etc/trafficserver configuration directory.
I think that this is a regression from 5.3.2 to 6.2.x and master. I found that in configs.cc, TSConfigDirGet() is no-longer used to check for a config file relative to etc/trafficserver.
I'm testing a patch to fix this.