mirror-update: switch fedora to kernel.org mirror

Our current mirror is out of sync, it has happened twice now.  It's
been several years since we switched away from kernel.org mirrors
(Ie6050fbf20259df39eab11f8e326d58351d98ea5) so it might be worth
trying again (they are currently in sync).  Also we are using the
".us" version here, to keep things more local to the update server.

Change-Id: I29cf3895e7fa8e401a1d686119e56b4fddb0cc47

playbooks/roles/mirror-update/files/fedora-mirror-update

@@ -26,14 +26,11 @@ else
 fi
 
 BASE="/afs/.openstack.org/mirror/fedora"
-# NOTE(pabelanger): #fedora-admin:
-# tibbs | I run pubmirror[12].math.uh.edu.
-# tibbs | It polls the masters every ten minutes.
 # NOTE(ianw): 2018-11 we dropped "-p" from the rsync commands
 #  because upstream starting putting setgid bits on directories,
 #  which you have to have admin permissions in AFS to set.
 #   https://pagure.io/releng/issue/7921
-MIRROR="rsync://pubmirror2.math.uh.edu/fedora-buffet/fedora/linux"
+MIRROR="rsync://mirrors.us.kernel.org/fedora"
 K5START="k5start -t -f /etc/fedora.keytab service/fedora-mirror -- ${TIMEOUT}"
 
 echo_ts "----- START FEDORA MIRROR RSYNC RUN -----"