Check for stale lock files

[HebaruSan]

This code change checks whether the registry lock file is stale before attempting to acquire the lock. This eliminates the lock file popup when it's not needed as per #2075, but keeps it when CKAN is actually still running.

I think there are race conditions if the user tries to start multiple copies of CKAN simultaneously; do we care about that?

Fixes #2075.

[politas]

The big question would have to be, does this work on Windows, too?

[HebaruSan]

Good point. I believe it would, but obviously what's needed is real testing. I'll take it for a spin on a Windows VM (which presumably will also involve installing KSP).

[politas]

I'm about to do so. You don't need a whole KSP, just the BuildID.txt and a GameData folder

[politas]

Seems to work fine on Windows, though it's much harder to get a real registry.locked file there.

[HebaruSan]

Yeah, wow, killing it with taskmgr cleans up the file, and it wouldn't even let me make a copy first. I'm vaguely curious as to how you managed it.

[politas]

A good setup for testing is a buildID.txt, a readme.txt, GameData and Ships directories.

buildID.txt just needs a valid build ID like so:

build id = 01804

(That's 1.3.0)

readme.txt is not needed other than to check the failover for bad buildIDs, and should have:

Version 1.3.0

(obviously, it's best to make the two files match as far as the version)

I just created a dummy registry.locked file with a four digit number (almost guaranteed not to exist)