[warden] Only add vcap user if it doesn't already exist
[warden] Only add vcap user if it doesn't already exist

Change-Id: I2a377cad14dc88f1c17fb36faecdb5e4e07ff00e

savaki/garden,tsaleh/garden,shashidharatd/garden-linux,savaki/garden,cloudfoundry-incubator/garden-linux,cloudfoundry-incubator/garden-linux,cloudfoundry-incubator/garden,tangfeixiong/garden,shashidharatd/garden-linux,cloudfoundry-incubator/garden,shashidharatd/garden-linux,tsaleh/garden,cloudfoundry-incubator/garden-linux,shashidharatd/garden-linux,tangfeixiong/garden