MiqWidget.available_for_user should check by both role and group.

https://bugzilla.redhat.com/show_bug.cgi?id=1158636
A widget's resource should be one of MiqReport, RssFeed or null.

So the checking of w.resource == user is not right and should be removed.
https://bugzilla.redhat.com/show_bug.cgi?id=1158636
Merge pull request #959 from lfu/widget_for_group_1158636

MiqWidget.available_for_user should check by both role and group.