Remove unused keystone params from neutron agents' config files

DHCP, L3 and Metadata agents' config files no longer need to
duplicate this info; it's available in neutron.conf

Change-Id: I7bea25d1c2b9249ddacce3f4638f7a8ed4f43197
cleanup potentially installed older oslo.config

If the user had oslo.config installed prior to us setting up the
oslo.config out of git they can get themselves into this very funny
situation where pip doesn't see oslo.config 1.1.x, however some
packages might. This manifests itself as a user error trying to
start nova-api which uses DeprecatedOption, not in oslo.config 1.1.x

Because of the funny state pip is in, you can't uninstall oslo.config.

So in these situations, if we see old oslo.config in the filesystem,
pip install / uninstall it to ensure that everyone ends up using the
git version instead.

To reduce the amount of user confusion, do this on every
install_oslo for a while, which we can purge after Havana ships.

Change-Id: If92073be5a431840701c952a194e63a7c452c9ca
Merge "Remove unused keystone params from neutron agents' config files"
Merge "cleanup potentially installed older oslo.config"