ve.init.mw.Target: Don't go into infinite recursion on API errors
The #tryWithPreparedCacheKey method was assuming that the request
could only fail because of invalid cache key. It can also fail because
of a bad token, and probably for a number of other reasons.
So only retry only once, and then fail. If it's a 'badtoken' error
during save, the caller will handle it and retry with a working token.
If it's something else, who knows, but we don't go into infinite loop
Failing in a way that will be handled is weird because 8e48f945 changed
the signatures of the promises, but not the functions that use them.
This must be fixed later.