Rely on the generator units for the rpc_pipefs mount
Closes: #1014429
The current behavior is slightly less worse in debian than in ubuntu. In Debian, if you install autofs and nfs-common together, you will get two mount points for rpc_pipefs. In Ubuntu, you get just one, but the wrong one (in /var/lib/nfs/rpc_pipefs). Someone hinted that this might be due to [3][4], but I didn't check that specifically.
I explained[5] in the Debian bug what I think is happening, and this PR is one way to address it, basically by getting rid of the duplication of the rpc_pipefs target and mount units and relying only on the generated ones. Consider this PR as a discussion point perhaps, so we can talk about specifics.
I pinged upstream[2] to see what they think, got one "unsure" reply so far.