DRY ActiveResource decode methods

[jistr]

A lot of the XML decode methods [1] will probably repeat itself across models, so we could extract it as common behavior.

[1] https://github.com/aeolus-incubator/thor-cli/blob/master/lib/aeolus_cli/model/provider.rb#L4-L29

EDIT after pblaho's comment:

Here's a permalink:

thor-cli/lib/aeolus/client/provider.rb

Lines 6 to 31 in e7b65db

	def decode(xml)
	if xml == nil or xml.size == 0
	return nil
	end
	if xml.start_with?('<providers>')
	h = ActiveResource::Formats.remove_root(Hash.from_xml(xml))
	# h is a hash of 'provider' => array of provider hashes
	if h['provider'].is_a?(Hash)
	# Having just one provider causes the value of 'provider' to
	# not exist in a array, so we wrap it in an array to prevent
	# an error like:
	# ...active_resource/base.rb:929:in `instantiate_collection':
	# undefined method `collect!' for #<Hash:0x0000000102e800> (NoMethodError)
	[h['provider']]
	else
	# return value is an array of hashes
	h['provider']
	end
	elsif xml.start_with?('<provider ') or xml.start_with?('<provider>')
	Hash.from_xml(xml)
	else
	# TODO raise an appropriate error that we didn't get <providers>
	# or <provider> xml
	nil
	end
	end

[petrblaho]

Link is no longer valid after renaming of files.

Here is new one - https://github.com/aeolus-incubator/thor-cli/blob/master/lib/aeolus/client/provider.rb#L6-L31