openqa: improve how we do the git config thing

The background to this is
https://bugzilla.redhat.com/show_bug.cgi?id=2073414 , in response
to which git was changed to die if a user runs git commands
on a repo which it doesn't own. In openQA, the test directory
is a git repo and openQA itself likes to run git commands on it,
but this is often going to be as a different user than the owner
of the directory. In fact on the worker hosts, the user that owns
the directory (geekotest on the server box) doesn't even exist.

This just sets the config by copying a file in place rather than
running a git command (which is hard to get to be idempotent) and
uses `/etc/gitconfig` so we don't wind up with a file in the
_openqa-worker user's home directory, which is meant to be empty.

Signed-off-by: Adam Williamson <awilliam@redhat.com>

roles/openqa/worker/files/gitconfig

@@ -0,0 +1,2 @@
+[safe]
+	directory = /var/lib/openqa/share/tests/fedora

roles/openqa/worker/tasks/main.yml

@@ -171,10 +171,7 @@
   when: openqa_tap|bool
 
 - name: Tell git it's OK for _openqa-worker to run 'git' on the test dir
-  command: git config --global --add safe.directory /var/lib/openqa/share/tests/fedora
-  become: yes
-  become_user: _openqa-worker
-  when: openqa_nfs_worker|bool
+  copy: src=gitconfig dest=/etc/gitconfig owner=root group=root mode=0644
 
 # this is kinda lazy - we could have a separate openqa_swtpm var so we
 # we could potentially separate tap worker hosts from swtpm ones - but