Update the base-roles test to use prepare-workspace-git

This is what this job should have been testing, as it's what we
recommend people use.  We simply didn't notice that OpenDev never
finished the transition away from use-cached-repos (which isn't
even defined in this repo).

Change-Id: I9be05f9c035441c3a0f84206b25580263663d179

test-playbooks/base-roles/base.yaml

@@ -6,7 +6,7 @@
 # Note: set-zuul-log-path-fact is tested by emit-job-header.yaml
 - include: emit-job-header.yaml
 - include: ensure-output-dirs.yaml
-- include: use-cached-repos.yaml
+- include: prepare-workspace-git.yaml
 - include: configure-mirrors.yaml
 - include: fetch-zuul-cloner.yaml
 - include: validate-host.yaml

test-playbooks/base-roles/prepare-workspace-git.yaml

@@ -1,7 +1,7 @@
-- name: Test the use-cached-repos role
+- name: Test the prepare-workspace-git role
   hosts: all
   roles:
-    - role: use-cached-repos
+    - role: prepare-workspace-git
   post_tasks:
     # opendev/base-jobs is in 'required-projects'.
     # Also check that the project being tested is being prepared.

zuul-tests.d/general-roles-jobs.yaml

@@ -113,14 +113,13 @@
     required-projects:
       - opendev/base-jobs
     files:
-      - ^roles/configure-mirrors/.*
       - ^roles/configure-mirrors/.*
       - ^roles/emit-job-header/.*
       - ^roles/ensure-output-dirs/.*
       - ^roles/fetch-output/.*
       - ^roles/fetch-zuul-cloner/.*
       - ^roles/set-zuul-log-path-fact/.*
-      - ^roles/use-cached-repo/.*
+      - ^roles/prepare-workspace-git/.*
       - ^roles/validate-host/.*
       - ^test-playbooks/base-roles/.*