CI: Add unit-test-race (#16470)

.drone.yml

@@ -217,6 +217,17 @@ steps:
       GITHUB_READ_TOKEN:
         from_secret: github_read_token
 
+  - name: unit-test-race
+    image: golang:1.16
+    commands:
+      - make test-backend
+    environment:
+      GOPROXY: off
+      TAGS: sqlite sqlite_unlock_notify
+      RACE_ENABLED: true
+      GITHUB_READ_TOKEN:
+        from_secret: github_read_token
+
   - name: unit-test-gogit
     pull: always
     image: golang:1.16