gitreview: Reorder and add padding.

Change-Id: I459dc320a8c9452a01eed6f403d786741587c890

.gitreview

 [gerrit]
+defaultbranch=master
+#
+# Intentional padding to ensure it is possible to point a commit
+# to an alternative gerrit server/repository without breaking
+# cherry-pick between branches.
+#
 host=gerrit.asterisk.org
 port=29418
 project=asterisk.git
-defaultbranch=master