We dump the list retriueved from LDAP at strstup in a temporary configuration
file and always use that file afterwards.
We check (possibly different) data from LDAP only at (re)start.
This way we always shutdown exactly the services we started even if the list
changed in the meanwhile (we avoid leaving a service running even if it was
removed from LDAP as the admin decided it should not be started in future).

This should also fix a problematic deadlock with systemd when we try to read
the list of service from LDAP at shutdown.

Simo.

* Adds ipa_memcached SystemV initscript

* Adds ipa_memcached service file and tmpfiles.d/ipa.conf
  to recreate /var/run/ipa_memcached on reboot.

* Adds ipa_memcached config file

* Adds memcacheinstnace.py to manage ipa_memcaced as
  as SimpleService object.

* Updates the IPA service list to include ipa_memcached,
  at service positon 39, httpd is position 40

* Updates the spec file:
  - requires the memcached daemon and python client
  - installs service or initscripts depending on OS
  - installs config file
  - creates /var/run/ipa_memcached directory

* Modifies ipa-server-install to install ipa_memcached