Add LBAAS_KEYSTONE_HOST to default conf

Add LBAAS_KEYSTONE_HOST, commented out, to the included
load-balancer.conf.
models/lbaas.rb: Rename tenant to tenantname

Rename the tenant parameter for the initialize and authentiate methods
to tenantname.
models/lbaas.rb: Better error handling in auth

Improve the error handling when parsing the tenants returned by
Keystone.
Update the documentation for monitors

BIGIP_MONITOR and LBAAS_MONITOR were replaced by MONITOR_NAME, and
MONITOR_PATH as added as well, so update the documentation to match.
Rewrite LBaaS keystone authentication

The LBaaS tenant and the Keystone tenant are not necessarily the same,
so add a new configuration option LBAAS_KEYSTONE_TENANT in addition to
the old LBAAS_TENANT option, and use its value for keystone authentication.

The username and password are only used for keystone authentication, so
rename the configuration options LBAAS_USERNAME to LBAAS_KEYSTONE_USERNAME
and LBAAS_PASSWORD to LBASS_KEYSTONE_PASSWORD.

Update the README and default .conf file accordingly.
Automatic commit of package [rubygem-openshift-origin-load-balancer-common] release [0.4-1].