[std-lib] validate_absolute_path does not detect malicious code injection

  $testpath = '/usr/bin/;rm -rf /;'

  validate_absolute_path($testpath)

  exec {

    "mkdir ${testpath}":

      returns => 0,

      user => 'root',

    ;

  }

  $testpath = '/*&^ foo\bar#baz /usr/bin/;rm -rf /;'

  validate_absolute_path($testpath)

  exec {

    "mkdir ${testpath}":

      returns => 0,

      user => 'root',

    ;

  }