puppet: make check for installed packages more reliable

"dpkg-query -s" doesn't necessarily provide the desired answer,
it includes packages known to dpkg for different reasons, but
does not exactly reply whether they are installed or not.

Starting with dpkg version 1.17.11 the ${db:Status-Status} +
${db:Status-Eflag} flags can be used for checking the current
state. While I don't think the puppet script is relevant for
Debian/wheezy systems (or even older) let's still be backwards
compatible.

Thanks: Manuel Montecelo for reporting
Thanks: Guillem Jover for feedback and code review

Development sponsored by Sipwise GmbH, recorded as
TT#25551 in customers' ticket system.

puppet/apply.sh

@@ -97,8 +97,28 @@ $IP $(hostname).example.org $(hostname)
   exit 1
 fi
 
+if dpkg --compare-versions "$(dpkg-query -f "\${Version}\n" -W dpkg 2>/dev/null)" ge '1.17.11' 2>/dev/null ; then
+  package_check() {
+    [ "$(dpkg-query -f "\${db:Status-Status} \${db:Status-Eflag}" -W "$package" 2>/dev/null)" = 'installed ok' ]
+  }
+else # dpkg versions older than 1.17.11 (e.g. Debian/wheezy) don't support db:Status* flags, so fall back then
+  package_check() {
+    dpkg --list "$package" 2>/dev/null | grep -q '^.i'
+  }
+fi
+
+package_installed() {
+  local packages="$*"
+
+  for package in $packages ; do
+    if ! package_check "$package" ; then
+      return 1
+    fi
+  done
+}
+
 if puppet apply jenkins_debian_glue.pp ; then
-  if ! dpkg-query -s jenkins jenkins-debian-glue >/dev/null 2>&1 ; then
+  if ! package_installed jenkins jenkins-debian-glue; then
     echo "While puppet reported a successful run, jenkins and/or jenkins-debian-glue aren't successfully installed. :(" >&2
     echo "Please re-execute this script and if the problem persists please report this at" >&2
     echo "https://github.com/mika/jenkins-debian-glue/issues" >&2