Synchronize keystone.conf template with Icehouse again

No real change this time.
Correctly set public_bind_host and admin_bind_host

Now that the bind_host setting has been split into public_bind_host and
admin_bind_host, we can use the correct attributes since we already had
this split in our attributes.

Note that, by default, it doesn't change anything as 0.0.0.0 is the
default values for both attributes.
Fix keystone config to use SQL driver for EC2Credential

This was lost in the update to Icehouse config.
Merge pull request #230 from vuntz/icehouse-conf

Synchronize keystone.conf template with Icehouse again
Merge pull request #231 from vuntz/fix-bind-hosts

Correctly set public_bind_host and admin_bind_host
Merge pull request #232 from vuntz/EC2Credential-driver

Fix keystone config to use SQL driver for EC2Credential