Fixed the crash when the accordions in compare/drift are clicked.

A setting for @keep_compare = true was missing for the panel_control
action causing @compare to have a nil value which was causing the crash.

https://bugzilla.redhat.com/show_bug.cgi?id=1114700
Merge pull request #119 from AparnaKarve/bz1102397_compare_drift_accordion_issue

Fixed the crash when the accordions in compare/drift are clicked.