Define separator explicitly in set_value call

set_value method of Puppet::Util::IniFile uses '' for separator when
called without the separator argument[1]. Set the argument explicitly
to avoid broken rendering. Note that the argument was added in
puppetlabs-inifile 2.0.0 so we don't need to bump the min version.

[1] puppetlabs/puppetlabs-inifile#544

Closes-Bug: #2081303
Change-Id: I6112c6d12e860bd4b4030e5f784952a7358f617f

lib/puppet/provider/swift_storage_policy/ruby.rb

@@ -104,7 +104,7 @@ def write_policy
     end
     self.class.policy_settings.each do |property_name, setting_name|
       unless @property_flush[property_name].nil?
-        config.set_value(policy_title, setting_name, @property_flush[property_name])
+        config.set_value(policy_title, setting_name, '=', @property_flush[property_name])
       end
     end
     config.save