Fix display file mode: in octal, not in decimal

Before:

$ ./cf-agent/cf-agent -KIf  ~/.cfagent/inputs/test.cf 
Running full policy integrity checks
 -> Created file /tmp/foo.txt, mode = 438 

After:
$ ./cf-agent/cf-agent -KIf  ~/.cfagent/inputs/test.cf 
Running full policy integrity checks
 -> Created file /tmp/foo.txt, mode = 666

test.cf:
body common control {
  bundlesequence => { "foo" };
  inputs  =>  { "cfengine_stdlib.cf" };
}

bundle agent foo {

  files:
    "/tmp/foo.txt"
      perms   =>  mog("666", "loic", "users"),
      create  =>  "true";
}