add mysql container to the build environment jenkins slave pod

Former-commit-id: ba0dff4c7aa838132eb36dff0c137b5f0fbb9126

ci/jenkins/pod/milvus-build-env-pod.yaml

@@ -20,3 +20,23 @@ spec:
       requests:
         memory: "16Gi"
         cpu: "4.0"
+
+---
+
+apiVersion: v1
+kind: Pod
+metadata:
+  name: milvus-mysql
+  labels:
+    app: milvus
+    componet: mysql
+spec:
+  containers:
+  - name: milvus-mysql
+    image: mysql:5.6
+    env:
+    - name: MYSQL_ROOT_PASSWORD
+      value: 123456
+    ports:
+    - containerPort: 3306
+      name: mysql