Revert "Fix userExists assertion for vcap ssh test"
Revert "Fix userExists assertion for vcap ssh test"

platform_test.userExists has different signature than
platform.userExists

This reverts commit 37ecbc86cba3f7bd5c64af12cc40eaf2e711f62c.

cloudfoundry/bosh-agent,cloudfoundry/bosh-agent,gu-bin/bosh-agent,gu-bin/bosh-agent,gu-bin/bosh-agent