L3 schedulers support

Icehouse brings new schedulers for virtual routing.
This patch aims to:
- add router_scheduler_driver flag support
- document which schedulers we could use

Cherry-pick notes:
  - Removed neutron.scheduler.l3_agent_scheduler.LeastRoutersScheduler
    from puppetdoc. It is not available in Havana.

Change-Id: I9ed4464201e1b888ae7474221babe8e5aad38642
Signed-off-by: Emilien Macchi <emilien.macchi@enovance.com>
(cherry picked from commit a57669a9dc3bacb80011ac45cf3da743de68e0bd)
Fixing neutron::server deprecated warnings

Clearing default values for deprecated reconnect_interval,
sql_idle_timeout, and sql_max_retries parameters.

Original Change-Id: I4b34e47dc9a814c0fbcc0fd6d8fe6033081a51d0
Closes-Bug: #1269623
(cherry picked from commit b14cee10c155c30dbf7b1645dfa095c4d5b0aa73)

Change-Id: Ib9ffc58fcb49c2c370950a1199878427e5a9efdb
Merge "L3 schedulers support" into stable/havana
Merge "Fixing neutron::server deprecated warnings" into stable/havana
Merge branch 'stable/havana' of https://github.com/stackforge/puppet-neutron into havana