Refactored implementation to make use of caching and to

limit the number of connections to external cobbler server for performance.
Added use of cobbler.ini file to configure settings.

Tested against Cobbler 2.4.0

plugins/inventory/cobbler.ini

+# Ansible Cobbler external inventory script settings
+#
+
+[cobbler]
+
+host = http://PATH_TO_COBBLER_SERVER/cobbler_api
+
+# API calls to Cobbler can be slow. For this reason, we cache the results of an API
+# call. Set this to the path you want cache files to be written to. Two files
+# will be written to this directory:
+#   - ansible-cobbler.cache
+#   - ansible-cobbler.index
+cache_path = /tmp
+
+# The number of seconds a cache file is considered valid. After this many
+# seconds, a new API call will be made, and the cache file will be updated.
+cache_max_age = 900
+
+
+