[as7] properly detect when we fail to read attribute, but still are connected and authenticated
Bug 1093374 - JON plugin for AS 7 cannot create an admin user in a moved
configuration directory

Original HostConfiguration#getSecurityPropertyFile is now deprecated, new
implementation takes ServerPluginConfiguration as a parameter instead of
baseDir and properly resovles 'relative-to' attribute value (according to
AS7 XSD Doc this value can be a any AS7 path name).
ServerPluginConfiguration has now method called getPath(String) which
accepts path-name and if known by plugin, appropriate File instance is
returned.