Revert "Add ipset element and hashsize tunables"

Revert "Add ipset element and hashsize tunables"

This reverts commit b5b919a7a3569ccb93c3d7d523c1edfaeddb7cb9.

The current ipset manager code isn't robust enough to handle
ipsets that already exist with different parameters. This reverts
the ability to change the parameters so we don't break upgrades
to Kilo.

Conflicts:
	neutron/agent/linux/ipset_manager.py
	neutron/tests/unit/agent/linux/test_ipset_manager.py

Change-Id: I538714df52424f0502cb75daea310517d1142c42
Closes-Bug: #1444201
(cherry picked from commit 03be14a569d240865dabff8b4c30385abf1dbe62)