[ovs-git] [openvswitch/ovs] 990ab7: travis: Fix OSX build on travis

[GitHub]

  Branch: refs/heads/branch-2.8
  Home:   https://github.com/openvswitch/ovs
  Commit: 990ab7c4dff02682d7453dafcbbc5bc3c524bed7
      https://github.com/openvswitch/ovs/commit/990ab7c4dff02682d7453dafcbbc5bc3c524bed7
  Author: William Tu <u9012063 at gmail.com>
  Date:   2017-11-01 (Wed, 01 Nov 2017)

  Changed paths:
    M .travis/osx-prepare.sh

  Log Message:
  -----------
  travis: Fix OSX build on travis

Run "brew update" before any installs.
This yields a clean build:
	https://travis-ci.org/williamtu/ovs-travis/builds/291616874

Signed-off-by: William Tu <u9012063 at gmail.com>
Acked-by: Yi-Hung Wei <yihung.wei at gmail.com>
Signed-off-by: Gurucharan Shetty <guru at ovn.org>