Pass strings to git_config module rather than have implicit conversion

This avoids the following warning:

[WARNING]: The value 0 (type int) in a string field was converted to u'0' (type
If this does not look like what you expect, quote the entire value to
ensure it does not change.

Change-Id: Ifaf4035b2101f6921182c3d3275554c7e5f4cfa2

tasks/repo_post_install.yml

@@ -17,7 +17,7 @@
   git_config:
     scope: system
     name: pack.threads
-    value: 0
+    value: '0'
 
 - name: Remove old key file(s) if found
   file: