only set permissions of files that exist
only set permissions of files that exist

Signed-off-by: Tony Hansmann <2c126519f2a6ad76296f425c3012060fde99f90e@pivotallabs.com>

mattcui/bosh-agent,Altoros/bosh-agent,gu-bin/bosh-agent,alex8023/bosh-agent,pivotal-nader-ziada/bosh-agent,allomov/bosh-agent,cloudfoundry/bosh-agent,jfuerth/bosh-agent,evanfarrar/bosh-agent,alex8023/bosh-agent,pivotal-nader-ziada/bosh-agent,jfuerth/bosh-agent,evanfarrar/bosh-agent,allomov/bosh-agent,mattcui/bosh-agent,tacgomes/bosh-agent,gu-bin/bosh-agent,pivotal-nader-ziada/bosh-agent,karafelix/bosh-agent,uzzz/bosh-agent,karafelix/bosh-agent,gu-bin/bosh-agent,allomov/bosh-agent,evanfarrar/bosh-agent,karafelix/bosh-agent,cloudfoundry/bosh-agent,tacgomes/bosh-agent,Altoros/bosh-agent,tacgomes/bosh-agent,Altoros/bosh-agent,alex8023/bosh-agent,uzzz/bosh-agent,mattcui/bosh-agent,uzzz/bosh-agent