tests: teach f not to report symlink mode bits

They're not meaningful or portable

tests/f

@@ -63,7 +63,7 b' def visit(opts, filenames, outfile):'
             stat = os.lstat(f)
             if opts.size and not isdir:
                 facts.append('size=%s' % stat.st_size)
-            if opts.mode:
+            if opts.mode and not islink:
                 facts.append('mode=%o' % (stat.st_mode & 0777))
             if opts.links:
                 facts.append('links=%s' % stat.st_nlink)

tests/test-tools.t

@@ -69,7 +69,7 b' Tests of the file helper tool'
   ./bar: file, size=21, mode=755, md5=3b03, sha1=612c
   ./baz: file, size=21, mode=755, md5=3b03, sha1=612c
   ./foo: file, size=4, mode=644, md5=d3b0, sha1=f1d2
-  ./l: link, size=5, mode=777, md5=2faa, sha1=af93
+  ./l: link, size=5, md5=2faa, sha1=af93
 #endif
 
   $ f --quiet bar -DL 3