The health observer test suite defines an assertSoon helper function, which by default waits for 10 seconds for the provided predicate to evaluate to true before failing the test. This is too short of a timeout to allow an observer to retry after hitting its own deadline timeout, which can make the tests susceptible to transient failures (e.g. the DNS health observer's deadline is 10 seconds as well).

We should increase this timeout to give the observers being tested a chance to retry, which should improve the stability of these tests.