slack-vitess-r12.0.5: allow conn overrides in consul topo

[timvaillancourt]

Description

NOTE: replaces PR #107

This PR allows overrides to http.Transport settings of the Consul topo client

This is to help address crashes we're seeing when too many consul connections are opened by vtctld

vtctld --help:

tvaillancourt@tvailla-ltmxctu vitess % ./vtctld --help 2>&1|grep -A1 topo_consul
  -topo_consul_idle_conn_timeout duration
    	Maximum amount of time to pool idle connections. (default 1m30s)
  -topo_consul_lock_delay duration
    	LockDelay for consul session. (default 15s)
  -topo_consul_lock_session_checks string
    	List of checks for consul session. (default "serfHealth")
  -topo_consul_lock_session_ttl string
    	TTL for consul session.
  -topo_consul_max_conns_per_host int
    	Maximum number of consul connections per host.
  -topo_consul_max_idle_conns int
    	Maximum number of idle consul connections. (default 100)
  -topo_consul_watch_poll_duration duration
    	time of the long poll for watch queries. (default 30s)

cc @rvrangel

Related Issue(s)

Checklist

• "Backport to:" labels have been added if this change should be back-ported
• Tests were added or are not required
• Did the new or modified tests pass consistently locally and on the CI
• Documentation was added or is not required

Deployment Notes