Require OBS_BACKEND_HOST to be set

Signed-off-by: Andrej Shadura <andrew.shadura@collabora.co.uk>

docker/backend-docker-entrypoint.sh

 #!/bin/sh
 
-if [ -z "$OBS_FRONTEND_HOST" ]; then
-    echo >&2 'error: OBS server frontend is unavailable and hostname option'
-    echo >&2 'is not specified '
-    echo >&2 '  You need to specify OBS_FRONTEND_HOST'
+if [ -z "$OBS_FRONTEND_HOST" ] || [ -z "$OBS_BACKEND_HOST" ]
+then
+    echo >&2 'You need to specify OBS_FRONTEND_HOST and OBS_BACKEND_HOST'
     exit 1
 fi
 
-HOSTNAME=$(hostname)
-
 if [ "$(stat -c %U /srv/obs/run)" != obsrun ]
 then
     echo "OBS files owned by the wrong user $(stat -c %U /srv/obs/run), re-owning..."
@@ -21,8 +18,8 @@ then
     cp /usr/lib/obs/server/BSConfig.pm.template /etc/obs/BSConfig.pm
 fi
 
-echo "Configure OBS backend host: ${HOSTNAME}"
-sed -i "s/hostname = .*/hostname = '${HOSTNAME}';/g" /etc/obs/BSConfig.pm
+echo "Configure OBS backend host: $OBS_BACKEND_HOST"
+sed -i "s/hostname = .*/hostname = '$OBS_BACKEND_HOST';/g" /etc/obs/BSConfig.pm
 
 echo "Configure OBS frontend host: ${OBS_FRONTEND_HOST}"
 sed -i "s/frontend = undef/frontend = '${OBS_FRONTEND_HOST}'/g" /etc/obs/BSConfig.pm