if a fact is present in two groups, it doesn't get cached if the second groups has a ttls

`fact_groups.conf` contains predefined groups. e.g.

{

...

"operating system": [

		"os",

                  ...

	],

...

}

and we can create our own groups in `facter.conf`
e.g.

facts : {

  ttls : [

    { "my_groups" : 30 days },

  ]

}

fact-groups : {

    my_groups: ["os.name"],

}

When both groups contain the same fact, the fact gets cached only if the first group has TTLS. On the other hand, if only the second group has ttls, the fact won't get cached (because it is found in the first group and the TTLS for the first groups does not exist)

FactGroups.get_fact_group is the method that detects the groups for a given fact.