Completion Suggester: Fix CompletionFieldMapper to correctly parse weight

[uschindler]

Followup for #3977:

if #3977 a check was added, that indexing completion suggester fields are rejected, if the weight is not an integer. My problem is that this check introduced there only works if the weight is a number. Unfortunately the parser has a bit strange logic: The new code is not executed if the client (creating the JSON) is passing the weight as "string", e.g. { "weight" : "10.5" }

In fact the weight is then ignored completely and not even an error is given (this is an additional bug in the parser logic). This caused me headaches yesterday, because the weight was given as JSON string in the indexing document. For other fields this makes no difference while indexing.

The parser for completion fields should be improved to have the outer check on the JSON key first and later check the types, not vice versa. This would also be consistent with indexing other fields, where the type of JSON value does not matter.

[s1monw]

@areek FYI I cherry-picked this commit into 1.4 as well I thing you missed it :)