Today when checking settings dependencies, we do not check if fallback
settings are present. This means, for example, that if
cluster.remote.*.seeds falls back to search.remote.*.seeds, and
cluster.remote.*.skip_unavailable and search.remote.*.skip_unavailable
depend on cluster.remote.*.seeds, and we have set search.remote.*.seeds
and search.remote.*.skip_unavailable, then validation will fail because
it is expected that cluster.ermote.*.seeds is set here. This commit
addresses this by also checking fallback settings when validating
dependencies. To do this, we adjust the settings exist method to also
check for fallback settings, a case that it was not handling previously.
9a404f3def