Fixes the following issues:
1. Use the right index when initializing the WriteOnlySet's vector of
atomics. Also switch to std::atomic_init to initialize each atomic in
the vector (cannot default construct the atomics in the vector
because std::atomic does not have a copy constructor).
2. Add failure check for when items cannot be inserted into the
WriteOnlySet due to capacity constraints. This situation occurs when
`copy` is not called on the WriteOnlySet, such as when sampling is
disabled. The `copy` function is what clears the WriteOnlySet.
3. Remove a global config feature I added to update the ClientDBInfo
object used by the global config listener function. This needs more
investigation, but the effect of this change could be that global
config changes are not correctly recognized on fdbserver processes.
4. Add various ASSERTs to verify data in WriteOnlySet.
