Hide the paging controls in Chargeback -> Assignments -> Storage

The call to the 'cb_rates_list' method applies to the Rates accordion
only and should not be called in explorer since that fetches the
chargeback rates list and displays a paging control at the bottom of
the 'Assignments' page where the paging controls are not applicable.

https://bugzilla.redhat.com/show_bug.cgi?id=1166187
Merge pull request #1109 from AparnaKarve/bz1166187_dont_display_pagecontrols_in_assignments

Hide the paging controls in Chargeback -> Assignments -> Storage