GOCBC-1048: Update collection manager error message parsing

Change-Id: I133849da35e25da3873fad5150070897aefb7233
Reviewed-on: http://review.couchbase.org/c/gocb/+/144367
Tested-by: Charles Dixon <chvckd@gmail.com>
Reviewed-by: Brett Lawson <brett19@gmail.com>

bucket_collectionsmgr.go

@@ -60,16 +60,16 @@ func (cm *CollectionManager) tryParseErrorMessage(req *mgmtRequest, resp *mgmtRe
 	errText := strings.ToLower(string(b))
 
 	if resp.StatusCode == 404 {
-		if strings.Contains(errText, "not found") && strings.Contains(errText, "scope") {
-			return makeGenericMgmtError(ErrScopeNotFound, req, resp)
-		} else if strings.Contains(errText, "not found") && strings.Contains(errText, "scope") {
+		if strings.Contains(errText, "not_found") && strings.Contains(errText, "collection") {
+			return makeGenericMgmtError(ErrCollectionNotFound, req, resp)
+		} else if strings.Contains(errText, "not_found") && strings.Contains(errText, "scope") {
 			return makeGenericMgmtError(ErrScopeNotFound, req, resp)
 		}
 	}
 
-	if strings.Contains(errText, "already exists") && strings.Contains(errText, "collection") {
+	if strings.Contains(errText, "already_exists") && strings.Contains(errText, "collection") {
 		return makeGenericMgmtError(ErrCollectionExists, req, resp)
-	} else if strings.Contains(errText, "already exists") && strings.Contains(errText, "scope") {
+	} else if strings.Contains(errText, "already_exists") && strings.Contains(errText, "scope") {
 		return makeGenericMgmtError(ErrScopeExists, req, resp)
 	}