Update go-txfile and dependencies

[urso]

• github.com/theckman/go-flock has been renamed to
  github.com/gofrs/flock
• go-txfile now relies on flock project on all platforms: Always creates
  a lock file
• go-txfile returns and error and does not block anymore if the lock file is
  taken

[ph]

LGTM, I've reviewed the other changes.

[urso]

@ph fyi; Partially improves #10653, but beats spooling support can not distinguish between starting a Beat or just testing some configuration. Instead of hanging, the test config command will return an error if the spool file is used by a concurrently running Beat. I wonder if this can affect the Agent.

[ph]

@ph fyi; Partially improves #10653, but beats spooling support can not distinguish between starting a Beat or just testing some configuration. Instead of hanging, the test config command will return an error if the spool file is used by a concurrently running Beat. I wonder if this can affect the Agent.

I think it could in a bad way, spooling to disk and upgrade path would be a pain. I need to create a followup issue on this problem.

[faec]

Testing notes (from conversation with @urso):

• check that events are still published if spooling to disk is enabled
• check a lock file is generated on linux/macOS
• starting a second beat using same spool file and running beat test config should not block but quit with an error