Add tools/conf/check_uptodate to tox.ini

To ensure that our sample config file, etc/ironic/ironic.conf.sample,
does not get out of sync with the code, this patch introduces a check
to tox that will compare the proposed ironic.conf.sample to a
freshly generated one, and error if they are not identical.

Ported from Nova's tools/config/check_uptodate.sh script.

Change-Id: Ic2898142754547e32bc4c03d23eca5d6a33721fc
Closes-bug: 1255621
Add config option for # of conductor replicas

Add hash_distribution_replicas option to ironic.common.hash_ring.

The consistent hash ring supports mapping to additional nodes around the
ring if some nodes may be temporarily offline. This option determines
how many nodes should be prepared in advance.

blueprint instance-mapping-by-consistent-hash

Change-Id: I93c2f735e201bbfb266e5a637fc76ddd5ca90e87