Remove 'apt-get upgrade' from Concourse main.tf
Remove 'apt-get upgrade' from Concourse main.tf

- Related to changes made in #1884962a3cc6165dc3fa043880847ada389f86b3
cloudfoundry-incubator/bosh-google-cpi-release,evandbrown/bosh-google-cpi-release,cloudfoundry-incubator/bosh-google-cpi-release,cloudfoundry-incubator/bosh-google-cpi-release,erjohnso/bosh-google-cpi-release,erjohnso/bosh-google-cpi-release,evandbrown/bosh-google-cpi-release,cloudfoundry-incubator/bosh-google-cpi-release,evandbrown/bosh-google-cpi-release,erjohnso/bosh-google-cpi-release,erjohnso/bosh-google-cpi-release,evandbrown/bosh-google-cpi-release