Two issues caused TestCollectPanic to flake:
1. ETXTBSY: The test exec'd the tailscaled binary directly without
going through StartDaemon/awaitTailscaledRunnable, so it lacked
the retry loop that other tests use to work around a mysterious
ETXTBSY on GitHub Actions.
2. Shared filch files: The test didn't pass --statedir or TS_LOGS_DIR,
so all parallel test instances wrote panic logs to the shared system
state directory (~/.local/share/tailscale). Concurrent runs would
clobber each other's filch log files, causing the second run to not
find the panic data from the first.
Fix both by adding awaitTailscaledRunnable before the first exec, and
passing --statedir and TS_LOGS_DIR to isolate each test's log files,
matching what StartDaemon does.
It now passes x/tools/cmd/stress.
Fixes#15865
Change-Id: If18b9acf8dbe9a986446a42c5d98de7ad8aae098
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
Brad Fitzpatrick
99bde5a406