pressure-vessel-wrap uses wrong hostname for xauth on OpenSUSE

I've found that newer Proton versions (official and Proton-GE) are failing to display anything on OpenSUSE. I've long been aware that OpenSUSE has some odd handling around xauth so I looked deeper into this. I gather it patches libxcb (among other things?) so that it creates an xauth entry against the shortened hostname rather than the FQDN, e.g. killstar rather than killstar.aura-online.co.uk. It also sets the XAUTHLOCALHOSTNAME environment variable to the shortened name accordingly. X11 applications fail to start when XAUTHLOCALHOSTNAME is not set correctly.

I noticed that write_xauth uses the nodename returned by uname to filter the entries in xauth_entry_should_propagate. This nodename is always the FQDN so it seemed likely that the applicable entry would be filtered out. Sure enough, I used nsenter to look at /run/user/1000/Xauthority within the isolated namespace and found that it was an empty file. Running xhost + allows things to work.

I therefore think that write_xauth should either use XAUTHLOCALHOSTNAME in preference to uname or it should check against both. I would fix this myself but OpenSUSE is my wife's system rather than my own and I lack the time or energy to get the development tools set up.