Don't run gtk-update-icon-cache when uninstalling the Qt package.  But do run
it when installing the gnome package.

Conflicts:
	packaging/rpm/SPECS/wireshark.spec.in

Change-Id: I0bbd9c0edc3fb6fe0e672aa3dbea5ba23d847d87
Reviewed-on: https://code.wireshark.org/review/5598
Reviewed-by: Jeff Morriss <jeff.morriss.ws@gmail.com>
(cherry picked from commit 7ef5abc818702a4699db39d183eb680bc3947eb4)
Reviewed-on: https://code.wireshark.org/review/5601