bug#61342: Quassel IRC service deletes nsfs mount on startup

[Riley Smith]

Since quassel is the only irc client that has been packaged as a guix 
service, I decided to give it a shot on my server. On the same server I 
also have installed some custom services to create a new net namespace, 
initialize it, and launch some programs inside it. After starting the 
quassel service I discovered that on startup it was removing the nsfs 
mount that I had previously created with `ip netns add`. To reproduce:

1. first add `(service quassel-service-type)` to your system config and 
do a guix system reconfigure

2. stop the quassel service, `herd stop quassel`

3. create a new net namespace named 'test' with a corresponding nsfs 
mount with `ip netns add test`

4. Verify that the nsfs mount is present by running `ip netns list` or 
check the /proc/mounts file for the presence of the nsfs mount at 
/var/run/netns/test

5. start the quassel service, `herd start quassel`

The nsfs mount should now be deleted, and running `ip netns list` will 
report "Error: Peer netns reference is invalid." This was tested on a 
clean install using the latest guix as of Feb 6th. This could be a 
quassel issue unrelated to guix, but I don't know when I'll have time to 
test quassel in a different distro so I wanted to make the issue now so 
others are aware that it exists.


-Riley