Support managing selinux

[wyardley]

When you give a datadir
you should on centos set the correct object

seltype => "mongod_var_lib_t",

(via https://tickets.puppetlabs.com/browse/MODULES-3444)

[alexjfisher]

Better might be to change the default context for that file path? Maybe using https://github.com/voxpupuli/puppet-selinux/blob/master/manifests/fcontext.pp, although there are some limitations to using that defined type instead of selinux::module.