Fix confidence bug (#360)

This PR fixed a bug when showing confidence in trigger definition. Confidence is usually a non-decreasing function on an interval. But we incorrectly only show confidence when the corresponding anomaly grade is larger than 0.

Testing done:
1. manually tested that the bug is fixed. See attached snapshots.
2. yarn test:jest

Signed-off-by: Kaituo Li <kaituo@amazon.com>

server/services/utils/__tests__/adHelpers.test.js

@@ -72,15 +72,15 @@ describe('helpers', () => {
             dataStartTime: 1587929940000,
             dataEndTime: 1587930000000,
             anomalyGrade: 0,
-            confidence: 0,
+            confidence: '0.99',
             plotTime: 1587929970000,
           },
           {
             detectorId: 'LNULDnEBdsd5fFw6Wr6N',
             dataStartTime: 1587930420000,
             dataEndTime: 1587930480000,
             anomalyGrade: 0,
-            confidence: 0,
+            confidence: '0.99',
             plotTime: 1587930450000,
           },
         ],

server/services/utils/adHelpers.js

@@ -22,7 +22,7 @@ export const anomalyResultMapper = (anomalyResults) => {
           ? Number.parseFloat(rest.anomalyGrade).toFixed(2)
           : 0,
       confidence:
-        rest.anomalyGrade != null && rest.anomalyGrade > 0
+        rest.confidence != null && rest.confidence > 0
           ? Number.parseFloat(rest.confidence).toFixed(2)
           : 0,
       plotTime: rest.dataStartTime + Math.floor((rest.dataEndTime - rest.dataStartTime) / 2),