82dd719 rpc: Write authcookie atomically (Wladimir J. van der Laan)
Pull request description:
Use POSIX rename atomicity at the `bitcoind` side to create a working cookie atomically: - Write `.cookie.tmp`, close file - Rename `.cookie.tmp` to `.cookie` This avoids clients reading invalid/partial cookies as in #11129. As such, this is an alternative to that PR.
Tree-SHA512: 47fcc1ed2ff3d8fed4b7441e4939f29cc99b57b7a035673c3b55a124a2e49c8a904637a6ff700dd13a184be8c0255707d74781f8e626314916418954e2467e03
Backport of Core PR11131
https://github.com/bitcoin/bitcoin/pull/11131/