Merge ~bjornt/maas:bug-1888536-2.8 into maas:2.8

[Björn Tillenius]

LP: #1888536 - named.conf.options.inside.maas reverts to default

run-named always generated a blank config for bind when it's started.

It's questionable why we need to do that on every start, but for now, we
don't generate a config if a config is alrady there.

This should be safe enough to backport, and then we can revisit this
later, to see if we can fix it in a better way.

(cherry picked from commit 192fd8b70d0524683a50f0510577bdb1dc89ec5a)

[Björn Tillenius (bjornt)]

Self-approve backport

review: Approve

[MAAS Lander (maas-lander)]

UNIT TESTS
-b bug-1888536-2.8 lp:~bjornt/maas/+git/maas into -b 2.8 lp:~maas-committers/maas

STATUS: SUCCESS
COMMIT: 7f34bda38bfe657fc8f837f0361de424883bbbfe

review: Approve

diff --git a/snap/local/tree/bin/run-named b/snap/local/tree/bin/run-named
index bd0c252..13c167c 100755
--- a/snap/local/tree/bin/run-named
+++ b/snap/local/tree/bin/run-named
@@ -12,6 +12,7 @@ cp -f "$SNAP/usr/share/maas/bind/named.conf" "$SNAP_DATA/bind/"
 mkdir -p "$SNAP_DATA/bind/cache"
 
 # generate MAAS bind configuration
-MAAS_DNS_CONFIG_DIR="$SNAP_DATA/bind" "$SNAP/bin/maas-rack" setup-dns
+MAAS_DNS_CONFIG_DIR="$SNAP_DATA/bind" "$SNAP/bin/maas-rack" \
+    setup-dns --no-clobber
 
 exec "$SNAP/usr/sbin/named" -c "$SNAP_DATA/bind/named.conf" -g