Add a failsafe script to import Seafile's APT key

utils/build/import-seafile-apt-key.sh

@@ -0,0 +1,27 @@
+#!/bin/bash
+
+# Docker Seafile client, help you mount a Seafile library as a volume.
+# Copyright (C) 2019, flow.gunso@gmail.com
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+not_imported=true
+while $not_imported; do
+	apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv-keys 8756C4F765C9AC3CB6B85D62379CE192D401AB61
+	if [ $? -eq 0 ]; then
+		not_imported=false
+	else
+		sleep 5
+	fi
+done