Fix base_environment for test to use 'hostname' instead of 'ip'. (#2920)
Fix base_environment for test to use 'hostname' instead of 'ip'. (#2920)

Since https://github.com/youtube/vitess/pull/2892 topodata.Tablet message
doesn't have the ip field anymore, the field hostname should be used instead.

While at it I'm also fixing get_tablet_ip_port() method to work properly if the
hostname contains IPv6 address.

BUG=62421941
sougou/vitess,pivanof/vitess,tinyspeck/vitess,mattharden/vitess,pivanof/vitess,HubSpot/vitess,tirsen/vitess,dcadevil/vitess,mahak/vitess,tirsen/vitess,rnavarro/vitess,vitessio/vitess,sougou/vitess,HubSpot/vitess,pivanof/vitess,dcadevil/vitess,dcadevil/vitess,tirsen/vitess,sougou/vitess,rnavarro/vitess,vitessio/vitess,enisoc/vitess,alainjobart/vitess,tinyspeck/vitess,davygeek/vitess,davygeek/vitess,enisoc/vitess,alainjobart/vitess,mattharden/vitess,tirsen/vitess,vitessio/vitess,tinyspeck/vitess,pivanof/vitess,tirsen/vitess,vitessio/vitess,tirsen/vitess,enisoc/vitess,tinyspeck/vitess,sougou/vitess,sougou/vitess,mattharden/vitess,tinyspeck/vitess,HubSpot/vitess,mahak/vitess,mahak/vitess,vitessio/vitess,pivanof/vitess,rnavarro/vitess,alainjobart/vitess,rnavarro/vitess,rnavarro/vitess,HubSpot/vitess,HubSpot/vitess,vitessio/vitess,mahak/vitess,tirsen/vitess,pivanof/vitess,mattharden/vitess,mattharden/vitess,enisoc/vitess,pivanof/vitess,mattharden/vitess,davygeek/vitess,pivanof/vitess,rnavarro/vitess,enisoc/vitess,davygeek/vitess,tinyspeck/vitess,sougou/vitess,tirsen/vitess,rnavarro/vitess,dcadevil/vitess,pivanof/vitess,vitessio/vitess,davygeek/vitess,alainjobart/vitess,mattharden/vitess,davygeek/vitess,alainjobart/vitess,enisoc/vitess,enisoc/vitess,rnavarro/vitess,HubSpot/vitess,mattharden/vitess,alainjobart/vitess,dcadevil/vitess,dcadevil/vitess,mahak/vitess,mattharden/vitess,mahak/vitess,HubSpot/vitess,mahak/vitess,davygeek/vitess,tinyspeck/vitess,mattharden/vitess,rnavarro/vitess,mahak/vitess,tirsen/vitess,alainjobart/vitess,vitessio/vitess,dcadevil/vitess,sougou/vitess,sougou/vitess,HubSpot/vitess,alainjobart/vitess