If calls to UserAgentServiceConnector fail then throw an exception. This lets the caller decide whether to discard the error or not.

This is Oren Hurvitz's 0001 patch from http://opensimulator.org/mantis/view.php?id=6956 but I ended up doing some tweaking to resolve patch application issues.
Change warns associated with UserAgentServiceConnector to debugs, as this is not necessarily a problen with the source simulator (e.g. someone else's remote simulator cannot be contacted).

This is Oren Hurvitz's second patch from http://opensimulator.org/mantis/view.php?id=6956 with a small amount of correction