Add github.com to the known_hosts
Add github.com to the known_hosts

- required for pull-request creation
- also checkout auto-update branch which is required
  for pull-request creation

[#149794797](https://www.pivotaltracker.com/story/show/149794797)

Signed-off-by: Tom Kiemes <2e6bc7bf64c2cabd57fd2be0c1baf57f97b6fecc@sap.com>

cloudfoundry-incubator/bosh-openstack-cpi-release,cloudfoundry-incubator/bosh-openstack-cpi-release,cloudfoundry-incubator/bosh-openstack-cpi-release