Import Zuul v3 job

Import the legacy-gitdm job and convert it to Zuul v3 native format.
Set it up to run in check and gate pipeline.

Previously the job was run in periodic pipeline every day as well. This
is not needed anymore, we use other tools nowadays.

Change-Id: I2876725c81d786a3f0edb7543927ffb520890607

.zuul.yaml

@@ -0,0 +1,14 @@
+- job:
+    name: gitdm-do-it
+    parent: unittests
+    description: |
+      Run do-it.sh for gitdm repository.
+    run: playbooks/do-it/run.yaml
+
+- project:
+    check:
+      jobs:
+        - gitdm-do-it
+    gate:
+      jobs:
+        - gitdm-do-it

playbooks/do-it/run.yaml

@@ -0,0 +1,14 @@
+- hosts: all
+
+  tasks:
+    - name: Run do-it.sh
+      shell:
+        cmd: |
+          set -e
+          set -x
+          export TEMPDIR=${TEMPDIR:-$(mktemp -d $(pwd)/dmtmp-XXXXXX)}
+          export GITBASE=${TEMPDIR}/git
+          export LP_STATS=n
+          bash ./do-it.sh
+        executable: /bin/bash
+        chdir: '{{ zuul.project.src_dir }}'