core: Permissions of group are not inherited when adding a user

When adding a user, the group_ids column at the users table
is not modified, so all the related stored procedures that
calculate the permissions do not calculate the correct set of
permissions.

Bug-Url: https://bugzilla.redhat.com/1065615
Change-Id: I47caf474fe9acfce26e6232a51918849d970f4cb
Signed-off-by: Yair Zaslavsky <yzaslavs@redhat.com>