The `XdsFaultInjectionMaxFault` test has seen a few flakes since #32326
was merged. I believe the flakiness is caused by the fact that when a
large number of RPCs are queued up before the resolver result comes in,
those RPCs are now re-processed in parallel instead of sequentially,
which can cause us to delay more RPCs than we should due to the
`max_faults` setting. To fix this, we change the test to ensure that the
channel is connected (i.e., the resolver result has already been
returned) before we start sending a large number of concurrent RPCs.
Although this is the only test that I've seen flakes in, I've made this
same change consistently to all fault injection tests that are creating
a large number of concurrent RPCs, since the same flake could affect any
of them.
e022a3dfa9