Add ipa_memcached service
    
    * 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