fix(scripts/debian): refinements to the scripts for DEB package

Co-authored-by: Lorenzo Fontana <lo@linux.com>
Signed-off-by: Leonardo Di Donato <leodidonato@gmail.com>

scripts/debian/postrm.in

@@ -0,0 +1,24 @@
+#!/bin/sh
+#
+# Copyright (C) 2019 The Falco Authors.
+#
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+set -e
+
+NAME=falco
+
+if [ "$1" = "purge" ] ; then
+	update-rc.d $NAME remove >/dev/null
+fi