MODULES-825: apache 2.4 mod_itk needs mod_prefork

in apache 2.4 mod_prefork can be installed along with mod_itk

On ubuntu 14.04 mod_itk library name is "mpm_itk.so" instead of "mod_mpm_itk.so".
Added an if statement that creates a symlink in case of a debian distro. this preserve old manifest behaviour in library loading while fixing ubuntu bug.

manifests/mod/itk.pp

@@ -13,8 +13,10 @@
   if defined(Class['apache::mod::peruser']) {
     fail('May not include both apache::mod::itk and apache::mod::peruser on the same node')
   }
-  if defined(Class['apache::mod::prefork']) {
-    fail('May not include both apache::mod::itk and apache::mod::prefork on the same node')
+  if versioncmp($apache_version, '2.4') < 0 {
+    if defined(Class['apache::mod::prefork']) {
+      fail('May not include both apache::mod::itk and apache::mod::prefork on the same node')
+    }
   }
   if defined(Class['apache::mod::worker']) {
     fail('May not include both apache::mod::itk and apache::mod::worker on the same node')

manifests/mod/prefork.pp

@@ -10,8 +10,10 @@
   if defined(Class['apache::mod::event']) {
     fail('May not include both apache::mod::prefork and apache::mod::event on the same node')
   }
-  if defined(Class['apache::mod::itk']) {
-    fail('May not include both apache::mod::prefork and apache::mod::itk on the same node')
+  if versioncmp($apache_version, '2.4') < 0 {
+    if defined(Class['apache::mod::itk']) {
+      fail('May not include both apache::mod::prefork and apache::mod::itk on the same node')
+    }
   }
   if defined(Class['apache::mod::peruser']) {
     fail('May not include both apache::mod::prefork and apache::mod::peruser on the same node')

manifests/mpm.pp

@@ -45,6 +45,13 @@
           before  => File[$::apache::mod_enable_dir],
           notify  => Service['httpd'],
         }
+
+        if $mpm == 'itk' {
+            file { "${lib_path}/mod_mpm_itk.so":
+              ensure  => link,
+              target  => "${lib_path}/mpm_itk.so"
+            }
+        }
       }
 
       if versioncmp($apache_version, '2.4') < 0 {