chore(java): install maven 3.8.1 at runtime (#1202) (#519)

Author: gcf-owl-bot[bot]

.github/.OwlBot.lock.yaml

@@ -1,3 +1,3 @@
 docker:
   image: gcr.io/repo-automation-bots/owlbot-java:latest
-  digest: sha256:2595f321d9a9acf34c2d02e4dc5ec214ce07eecdb43978382d8a88476dec0c16
+  digest: sha256:4837f2a7fdff2985b4f7432f8a6d6a87beacebf3ac071746532c0ce2e3f24b9b

.github/workflows/ci.yaml

@@ -12,6 +12,9 @@ jobs:
         java: [8, 11]
     steps:
     - uses: actions/checkout@v2
+    - uses: stCarolas/setup-maven@v4
+      with:
+        maven-version: 3.8.1
     - uses: actions/setup-java@v1
       with:
         java-version: ${{matrix.java}}
@@ -37,6 +40,9 @@ jobs:
         java: [8, 11]
     steps:
     - uses: actions/checkout@v2
+    - uses: stCarolas/setup-maven@v4
+      with:
+        maven-version: 3.8.1
     - uses: actions/setup-java@v1
       with:
         java-version: ${{matrix.java}}
@@ -46,6 +52,9 @@ jobs:
     runs-on: ubuntu-latest
     steps:
     - uses: actions/checkout@v2
+    - uses: stCarolas/setup-maven@v4
+      with:
+        maven-version: 3.8.1
     - uses: actions/setup-java@v1
       with:
         java-version: 8
@@ -57,10 +66,13 @@ jobs:
     runs-on: ubuntu-latest
     steps:
     - uses: actions/checkout@v2
+    - uses: stCarolas/setup-maven@v4
+      with:
+        maven-version: 3.8.1
     - uses: actions/setup-java@v1
       with:
         java-version: 8
     - run: java -version
     - run: .kokoro/build.sh
       env:
-        JOB_TYPE: clirr
+        JOB_TYPE: clirr