- add () to function to actually disconnect from p2pconn
- extract max interval into a constant
- disconnect at the end of a subtest rather than start of next
This is a backport of Core [[https://github.com/bitcoin/bitcoin/pull/18807 | PR18807]] [2/9]
https://github.com/bitcoin/bitcoin/pull/18807/commits/bd093ca15de762fdaf0937a0877d17b0c2bce16e