08ce33f8e qa: Move wait_until to util (MarcoFalke)
Pull request description:
This moves `wait_until` to `util.py` to make it generally available to python tests.
Also, `wait_until` now takes an optional lock that is acquired while testing the predicate.
Previously the lock was always acquired, even when it was not necessary, cf. `disconnect_ban.py`.
Tree-SHA512: 18e452a017a6566fa8ad09bde058e1b841e167039dc63299e70cfa7a6dcbc779581e60ca3e8eb2f1b610767d5208b9376c203eb11015b250fd0542b5eb4215a8
329ac3b [tests] use wait_until in mempool_persist.py (John Newbery)
Tree-SHA512: 3f5fe3dcdb5da3b10a41f7b88d29c15b79c02fbb037914b4342b77428f2afe8b342f6adacb28a9eb5549aa156cd146175389bd61909a20df3fecb88361c4779f
a750d77 Add tests for mempool persistence (John Newbery)
91c91e1 Control mempool persistence using a command line parameter. (John Newbery)
Tree-SHA512: 157d01cefd1903b8bfc5cbab42a3cc5e9c1094179bf4b64b3d34c0d4d9b976d593755bfea5c41c631cb758e1de17c6c2058c130d487d20560b7c0bafcddfa520