When Find unavailable, initialization needs better error handling

Description

The current fix in Find Commerce is to catch WebExceptions, but there are cases when ServiceExceptions will be thrown as well. For details, see https://www.brianweet.com/2018/03/20/unstable-episerver-find-developer-indexes.html.

We should ensure that ServiceException is handled as well. Since we already have the episerver:findcommerce.IgnoreWebExceptionOnInitialization app setting for this, we will reuse that. The name is a slight mismatch, but it is not worth introducing another setting or breaking the configuration by renaming it.