test(network): give the reconnect test a budget above the backoff (backport of #4569)

[stevenvegt]

Backport of #4569.

Problem

TestNetworkIntegration_OutboundConnection11Reconnects fails intermittently under load with "time-out while waiting for node 1 to reconnect to node 2".

The test restarts node2 and gives node1 defaultTimeout, 5 seconds, to reconnect by itself. That reconnect races the backoff: when a connection that was up is closed cleanly, connect() resets the backoff to RandomBackoff(time.Second, 5*time.Second), and connectLoop only picks up expired backoffs on a one second ticker. The worst case is therefore already over the budget before dialling and the TLS handshake start.

This is not new and is not caused by any recent change. The random reset came in with #1874 (2023-02-24) and defaultTimeout predates it.

Change

The reconnect wait gets its own budget of 15 seconds, with the arithmetic written down next to the constant. The two other waits in the test are an initial connect and a disconnect, neither of which races a backoff, so they keep defaultTimeout.

Test-only, no production code touched. Cherry-picked without conflicts.

Verification

This is a timing budget, so there is no deterministic RED: the test passes before and after when the machine is quiet. -count=5 passes on this branch. What the change removes is a worst case that was outside the budget by construction, visible in the two constants rather than in a test run.