selmodule provider should only list modules once

With a selmodule resource such as:

selmodule { 'test': 

  ensure => present, 

  selmodulepath => '/usr/share/selinux/test.pp', 

  syncversion => true, 

}

The provider runs semodule --list twice, once for exists? and once for syncversion:

Debug: Selmodule[test](provider=semodule): Checking for module test 

Debug: Executing '/usr/sbin/semodule --list' 

Debug: Selmodule[test](provider=semodule): Checking syncversion on test 

Debug: Executing '/usr/sbin/semodule --list' 

Debug: Selmodule[test](provider=semodule): load version 1.1 

Debug: Selmodule[test](provider=semodule): file version 1.1 

The semodule --list command takes around 2-3 seconds to execute, which causes a large performance hit when there are multiple selmodule resources.

This impact could be cut in half if the command was only run once and the data cached for the syncversion function. It could be cut even more dramatically if semodule --list was stored as a fact and the output merely referenced in the provider.