Change pushkin ip address

Avoid the openvpn routing conflict when using 192.168.100.2

Related to T3460

Test Plan

diff origin/production/pergamon.softwareheritage.org current/pergamon.softwareheritage.org
*******************************************
  Concat::Fragment[icinga2::object::Host::pushkin.internal.softwareheritage.org] =>
   parameters =>
     content =>
      @@ -1,5 +1,5 @@
      _
       object Host "pushkin.internal.softwareheritage.org" {
      -  address = "192.168.100.2"
      +  address = "192.168.100.4"
         display_name = "pushkin.internal.softwareheritage.org"
         check_command = "hostalive"
*******************************************
  Concat_fragment[icinga2::object::Host::pushkin.internal.softwareheritage.org] =>
   parameters =>
     content =>
      @@ -1,5 +1,5 @@
      _
       object Host "pushkin.internal.softwareheritage.org" {
      -  address = "192.168.100.2"
      +  address = "192.168.100.4"
         display_name = "pushkin.internal.softwareheritage.org"
         check_command = "hostalive"
*******************************************
  Icinga2::Object::Host[pushkin.internal.softwareheritage.org] =>
   parameters =>
     address =>
      - 192.168.100.2
      + 192.168.100.4
*******************************************
  Icinga2::Object[icinga2::object::Host::pushkin.internal.softwareheritage.org] =>
   parameters =>
     attrs =>
       address =>
        - 192.168.100.2
        + 192.168.100.4
*******************************************
  Resource_record[pushkin/A+PTR] =>
   parameters =>
     record =>
      - 2.100.168.192.in-addr.arpa
      + 4.100.168.192.in-addr.arpa
*******************************************
  Resource_record[pushkin/A] =>
   parameters =>
     data =>
      - 192.168.100.2
      + 192.168.100.4
*** End octocatalog-diff on pergamon.softwareheritage.org

---

Migrated from D6060 (view on Phabricator)