Previously this was a configuration field.
Ports `maxAllowedFailures()` from `determineMaxAllowedFailures()` in
#7794.
Test updates:
Remove the `maxRemoteFailures` param from `setup` in all VA tests.
Some tests were depending on setting this param directly to provoke
failures.
For example, `TestMultiVAEarlyReturn` previously relied on "zero allowed
failures". Since the number of allowed failures is now 1 for the number
of remote VAs we were testing (2), the VA wasn't returning early with an
error; it was succeeding! To fix that, make sure there are two failures.
Since two failures from two RVAs wouldn't exercise the right situation,
add a third RVA, so we get two failures from three RVAs.
Similarly, TestMultiCAARechecking had several test cases that omitted
this field, effectively setting it to zero allowed failures. I updated
the "1 RVA failure" test case to expect overall success and added a "2
RVA failures" test case to expect overall failure (we previously
expected overall failure from a single RVA failing).
In TestMultiVA I had to change a test for `len(lines) != 1` to
`len(lines) == 0`, because with more backends we were now logging more
errors, and finding e.g. `len(lines)` to be 2.
a46c388f66