starting via system proxy fails

[Antoine Martin]

For just a simple xpra start --start=xterm with or without ssh (first reported for an ssh start via IRC).

The xpra early startup log is full of:

No protocol specified

As we try to open the vfb display to verify that it has started OK.
I'm pretty sure this used to work fine not so long ago.

It may be related to XAUTHORITY.
root used to be able to access the display, maybe not any more?

To make it easier to debug, I tested with start-via-proxy=yes so we don't retry without the proxy and clobber the log files.

SSH start is worse, because we take so long to timeout that we may not have time to try without the system proxy before the client gives up.

Links:

• ​No protocol specified - cannot open display: :0.0
• some suggestions of turning off authentication with "-ac" to verify that the problem is authentication related

[Antoine Martin]

Fix is in r17960. For older branches, use r17963.

Something must have changed with the xauth handling to cause this breakage. (our code was wrong but was succeeding anyway!)

@shimm: does that work for you?