edge case: halt height too close to the upgrade height

[mkaczanowski]

TL;DR

Blazar may get stuck if the node restarted (due to halt height) too close to the upgrade height. In such case, chain watcher may miss the block at which it should execute the pre-check, thus will get stuck waiting for the block till timeout expires.

The trick is that restart of a node takes some time (gated by timeout expressed in time.Duration) and the pre-checks are expressed in number of blocks.

There should be a good integration test to cover such case