ftpd: add basic wildcard support

this is the minimal implementation to allow mget and similar commands with
wildcards.

We only support wildcard for the last path level, for example:

- mget *.xml is supported
- mget dir/*.xml is supported
- mget */*.xml is not supported

Removed . and .. from FTP directory listing

Signed-off-by: Nicola Murino <nicola.murino@gmail.com>

ftpd/cryptfs_test.go

@@ -57,9 +57,9 @@ func TestBasicFTPHandlingCryptFs(t *testing.T) {
 		}
 		list, err := client.List(".")
 		if assert.NoError(t, err) {
-			assert.Len(t, list, 2)
-			assert.Equal(t, ".", list[0].Name)
-			assert.Equal(t, testFileSize, int64(list[1].Size))
+			if assert.Len(t, list, 1) {
+				assert.Equal(t, testFileSize, int64(list[0].Size))
+			}
 		}
 		user, _, err = httpdtest.GetUserByUsername(user.Username, http.StatusOK)
 		assert.NoError(t, err)