virjson: Change virJSONValueObjectHasKey() signature

virjson: Change virJSONValueObjectHasKey() signature

Currently, virJSONValueObjectHasKey() can return one of three
values:

  -1 if passed object type is not VIR_JSON_TYPE_OBJECT,
   0 if the key is not present, and finally
   1 if the key is present.

But, neither of callers is interested in the -1 case. In fact,
some callers call this function treating -1 and 1 cases the same.
Therefore, make the function return just true/false and fix few
callers that explicitly checked for == 1 case.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Peter Krempa <pkrempa@redhat.com>