Mocha integration tests don't exit after finishing

[adespawn]

This is probably related to https://boneskull.com/mocha-v4-nears-release/#mochawontforceexit
It's likely currently tests don't clean up properly after themself. This is "fixed" by using --exit flag but it doesn't seem to be the intended way. Since 2018.

[adespawn]

It appears, that with the current state of the code, the problem is fixed. My theory is that the old code required tests to call shutdown for the program to exit correctly, which is no longer the case

[adespawn]

For some unknown reasons, this problem appeared again.