GODRIVER-3445 Update system setup to use task for git submodule init

Author: prestonvasquez

.evergreen/config.yml

@@ -32,11 +32,6 @@ functions:
       type: system
       params:
         directory: src/go.mongodb.org/mongo-driver
-    - command: shell.exec
-      params:
-        working_dir: "src/go.mongodb.org/mongo-driver"
-        script: |
-          git submodule update --init
     # Make an env.sh and evergreen expansion file with dynamic values
     - command: subprocess.exec
       params:
@@ -49,6 +44,10 @@ functions:
           # Define an alias for the task runner script.
           TASK_RUNNER_ALIAS: &task-runner src/go.mongodb.org/mongo-driver/.evergreen/run-task.sh
         args: [.evergreen/setup-system.sh]
+    - command: subprocess.exec
+      params:
+        binary: bash
+        args: [*task-runner, init-submodule]
     - command: expansions.update
       params:
         file: src/go.mongodb.org/mongo-driver/expansion.yml