Add missing postinst steps to Ubuntu

The following post install steps were missing on Ubuntu builds:

- Permission fixes
- sysctl load
- Service restart
- confluent PAM symlink to /etc/pam.d/sshd. It works without it on
  Ubuntu because it falls back to other which allows login on Ubuntu,
  but the behaviour should be the same on every OS. Furtheremore, an
  admin might implement additional steps to sshd PAM and would like to
  have this in Confluent, too

confluent_server/builddeb

@@ -50,12 +50,30 @@ if ! grep wheezy /etc/os-release; then
 fi
 head -n -1 debian/control > debian/control1
 mv debian/control1 debian/control
-cat > debian/postinst << EOF
-if ! getent passwd confluent > /dev/null; then 
+cat > debian/postinst << \EOF
+if ! getent passwd confluent > /dev/null; then
     useradd -r confluent -d /var/lib/confluent -s /usr/sbin/nologin
-    mkdir -p /etc/confluent
-    chown confluent /etc/confluent
 fi
+mkdir -p /etc/confluent /var/lib/confluent /var/log/confluent /var/cache/confluent
+chown confluent:confluent /etc/confluent /var/lib/confluent /var/log/confluent /var/cache/confluent
+
+sysctl -p /usr/lib/sysctl.d/confluent.conf > /dev/null 2>&1
+NEEDCHOWN=0
+NEEDSTART=0
+[ -n "$(find /etc/confluent /var/log/confluent /var/cache/confluent -uid 0 -print -quit 2>/dev/null)" ] && NEEDCHOWN=1
+if [ $NEEDCHOWN = 1 ]; then
+    if systemctl is-active confluent > /dev/null; then
+        NEEDSTART=1
+        systemctl stop confluent
+    fi
+    chown -R confluent:confluent /etc/confluent /var/log/confluent /var/cache/confluent
+fi
+systemctl daemon-reload
+if systemctl is-active confluent > /dev/null || [ $NEEDSTART = 1 ]; then systemctl restart confluent > /dev/null 2>&1; fi
+if [ ! -e /etc/pam.d/confluent ]; then
+    ln -s /etc/pam.d/sshd /etc/pam.d/confluent
+fi
+true
 EOF
 echo 'export PYBUILD_INSTALL_ARGS=--install-lib=/opt/confluent/lib/python' >> debian/rules
 #echo 'Provides: python-'$DPKGNAME >> debian/control