Improper use of error_log in sf_queue_handle_upserts

There are a number of calls to error_log in sf_queue which appear to be dumping debug output to the PHP error log. This creates a large amount of un-necessary chatter in the error log and should really be done with Devel's dd() or something similar.

If I get time I'll create a patch to remove them and possibly add some additional Salesforce logging in the watchdog where appropriate.