Only inspect file attribute if lsattr(1) is installed

[eradman]

What does this PR do?

lsattr/chattr is not installed on many Unix-like platforms by default, including *BSD, Solaris, and minimal Linux distributions such as Alpine. Skip attribute checks if lsattr is not found.

Previous Behavior

file.check_perms and anything that invokes it such as state.highstate fails:

$ doas salt-call --local --file-root=$PWD file.check_perms /tmp/file '{}' eradman users 644
Error running 'file.check_perms': Unable to run command '['lsattr', '/tmp/file']' with the context '{...}', reason: command not found

New Behavior

An error calling chattr is only raised if attributes were specified

Tests written?

No, but tested on OpenBSD 6.1 and CentOS 7.3. This is Cent7:

$ sudo -E salt-call -l debug --local --file-root=$PWD file.check_perms /tmp/file '{}' radman users 644 ai
local:
    |_
      ----------
      changes:
          ----------
          attrs:
              ai
      comment:
      name:
          /tmp/file
      result:
          True
    |_
      ----------
      lattrs:
          a
      lgroup:
          users
      lmode:
          0644
      luser:
          radman

[ghost]

@eradman, thanks for your PR! By analyzing the history of the files in this pull request, we identified @terminalmage, @whiteinge and @techhat to be potential reviewers.