update 6.0 branch esvm to 6.0.0

[LeeDr]

Kibana version: 6.0.0

Elasticsearch version: should be 6.0.0 but esvm is getting 6.0.0-rc1

Server OS version: Windows

Browser version:

Browser OS version:

Original install method (e.g. download page, yum, from source, etc.): source

Description of the problem including expected versus actual behavior:
When I start npm run test:ui:server esvm downloads and starts Elasticsearch. I think it should use a build from the same version as Kibana (currently 6.0.0) but is getting an older 6.0.0-rc1

Steps to reproduce:

1. checkout kibana 6.0 branch
2. npm install
3. npm run test:ui:server

Errors in browser console (if relevant):

Provide logs and/or server output (if relevant):
Running "esvm:ui" (esvm) task
starting up "ui" cluster
INFO - - cluster - Downloading & installing from "6.0" branch.
INFO - - cluster - Installing plugins
INFO - - cluster - Purging C:\git\master\kibana\esvm\test\branch-6.0\data
INFO - - cluster - Starting 1 nodes
INFO - ? - ? - [2017-11-07T15:30:01,371][INFO ][o.e.n.Node ] [] initializing ...
INFO - LI4cL2O - node_environment - using [1] data paths, mounts [[OS (C:)]], net usable_space [10.2gb], net total_space [189.4gb], types [NTFS]
INFO - LI4cL2O - node_environment - heap size [989.8mb], compressed ordinary object pointers [true]
INFO - ? - ? - [2017-11-07T15:30:02,029][INFO ][o.e.n.Node ] node name [LI4cL2O] derived from node ID [LI4cL2OBSna1v_mT9fPehQ]; set [node.name] to override
INFO - ? - ? - [2017-11-07T15:30:02,030][INFO ][o.e.n.Node ] version[6.0.0-rc1-SNAPSHOT], pid[29432], build[6f57a84/2017-09-01T18:07:02.565Z], OS

[jbudz]

Blocked pending #14281 and #14310.

[jbudz]

my bad, those are for 6.x/7.0

[tylersmalley]

6.0 has been bumped