CollectionLock acquisition in shard_filtering_metadata_refresh.cpp can cause server to terminate on stepdown

The CollectionLock acquisition in onShardVersionMismatch() can throw (for example, due to interrupt on stepdown), but it's called from the catch block in service_entry_point_common.cpp (and there is no try/catch above this point), so if it throws the exception will terminate the server.

We could either put an UninterruptibleLockGuard or try/catch around the lock acquisition; it may be better to put a try/catch, since we probably don't want to block stepdown for this.