This patch adding option to control weight of haproxy
backends per service via host variable.
Example:
[control]
server1 haproxy_nova_api_weight=10
server2 haproxy_nova_api_weight=2 haproxy_keystone_internal_weight=10
server3 haproxy_keystone_admin_weight=50
If weight is not defined, everything is working as before.
Change-Id: Ie8cc228198651c57f8ffe3eb060875e45d1f0700