vtgate/buffer: Reduce --vtgate_buffer_min_time_between_failovers default value from 5 to 1 minutes.
vtgate/buffer: Reduce --vtgate_buffer_min_time_between_failovers default value from 5 to 1 minutes.

After internal discussions, it's not unlikely that a second failover for the same shard could happen after a minute.

BUG=26755052

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