Purge syn cookies from thread #959

Job	Run time
Linux [UBSAN] [lmdb \| clang]	38m 17s
Linux [ASAN] [lmdb \| clang]	24m 3s
Linux [ASAN_INT] [lmdb \| clang] (Errors Ignored)	26m 43s
macOS [UBSAN] [lmdb \| clang]	36m 57s
macOS [ASAN] [lmdb \| clang]	27m 20s
Linux [TSAN] [lmdb \| clang] (Errors Ignored)	13m 23s
Linux [LEAK] [lmdb \| clang] (Errors Ignored)	38m 34s
macOS [TSAN] [lmdb \| clang] (Errors Ignored)	31m 34s
macOS [UBSAN] [rocksdb \| clang]	39m 10s
Linux [UBSAN] [rocksdb \| clang]	44m 13s
macOS [ASAN] [rocksdb \| clang]	37m 3s
Linux [ASAN] [rocksdb \| clang]	24m 36s
Linux [ASAN_INT] [rocksdb \| clang] (Errors Ignored)	53m 6s
macOS [TSAN] [rocksdb \| clang] (Errors Ignored)	59m 5s
Linux [TSAN] [rocksdb \| clang] (Errors Ignored)	14m 1s
Linux [LEAK] [rocksdb \| clang] (Errors Ignored)	46m 4s
	9h 14m 9s

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