Generate self-signed cert in /etc/ssl/private/kasmvnc.pem

I piggyback on ssl-cert package that's got ssl-cert group and the
directory /etc/ssl/private, the group can read files from (but not list
files there). Thus, by adding a user to ssl-cert group, they can read
both ssl-cert certificates and the KasmVNC certificate.o

Note: currently, KasmVNC only supports one file that must contain both
private and public keys. For this reason, I didn't use the snakeoil
certificate from ssl-cert, as it's split into two files.

debian/postrm

@@ -0,0 +1,40 @@
+#!/bin/sh
+# postrm script for kasmvnc
+#
+# see: dh_installdeb(1)
+
+set -e
+
+# summary of how this script can be called:
+#        * <postrm> `remove'
+#        * <postrm> `purge'
+#        * <old-postrm> `upgrade' <new-version>
+#        * <new-postrm> `failed-upgrade' <old-version>
+#        * <new-postrm> `abort-install'
+#        * <new-postrm> `abort-install' <old-version>
+#        * <new-postrm> `abort-upgrade' <old-version>
+#        * <disappearer's-postrm> `disappear' <overwriter>
+#          <overwriter-version>
+# for details, see https://www.debian.org/doc/debian-policy/ or
+# the debian-policy package
+
+
+case "$1" in
+    purge)
+      rm -r /etc/ssl/private/kasmvnc.pem
+    ;;
+    purge|remove|upgrade|failed-upgrade|abort-install|abort-upgrade|disappear)
+    ;;
+
+    *)
+        echo "postrm called with unknown argument \`$1'" >&2
+        exit 1
+    ;;
+esac
+
+# dh_installdeb will replace this with shell code automatically
+# generated by other debhelper scripts.
+
+#DEBHELPER#
+
+exit 0