Remove qemu-img rootwrap filter

It should be managed by ironic-lib.

Change-Id: I1b17982fdab5611086f8bb7d944db6f51bb032a0

etc/ironic/rootwrap.d/ironic-images.filters

@@ -1,6 +0,0 @@
-# ironic-rootwrap command filters to manipulate images
-# This file should be owned by (and only-writable by) the root user
-
-[Filters]
-# ironic/common/images.py: 'qemu-img'
-qemu-img: CommandFilter, qemu-img, root