GOCBC-1111: On status 200 parse any search errors from the status object

Motivation
-----------
Search can reply with a status code of 200 but still have errors which
are recorded in the status object. At present we try to parse these
errors from the top level object instead.

Changes
--------
Update search response json parsing so that the errors field is parsed
from within the status object.

Change-Id: I2e4caaf5ee955fba04b9679a866020c0e5872fa0
Reviewed-on: http://review.couchbase.org/c/gocb/+/155195
Reviewed-by: Brett Lawson <brett19@gmail.com>
Tested-by: Charles Dixon <chvckd@gmail.com>

cluster_searchquery.go

@@ -61,8 +61,12 @@ type jsonSearchRow struct {
 	Fields      json.RawMessage        `json:"fields"`
 }
 
+type jsonSearchResponseStatus struct {
+	Errors map[string]string `json:"errors"`
+}
+
 type jsonSearchResponse struct {
-	Errors    map[string]string          `json:"errors"`
+	Status    jsonSearchResponseStatus   `json:"status,omitempty"`
 	TotalHits uint64                     `json:"total_hits"`
 	MaxScore  float64                    `json:"max_score"`
 	Took      uint64                     `json:"took"`
@@ -100,7 +104,7 @@ func (meta *SearchMetaData) fromData(data jsonSearchResponse) error {
 	}
 
 	meta.Metrics = metrics
-	meta.Errors = data.Errors
+	meta.Errors = data.Status.Errors
 
 	return nil
 }