Also throw in various nits.
Backport Core PR #11078: [tests] Make p2p-leaktests.py more robust
0063d2c3d [tests] Make p2p-leaktests.py more robust (John Newbery)
Pull request description:
There has been an example of p2p-leaktests.py failing on travis in the new service bits test (introduced in #11001 . It appeared to me that the previous p2p connections had not been fully disconnected before attempting to add new p2p connections. I've added a sleep and restarted the NetworkThread, but I don't know whether this will fix the problem, since I'm unable to reproduce the failure locally.