We enable symlink support using the --links command line switch.
On the VFS layer, symlinks always ends with the rclonelink suffix.
This is because it is what we send/get to/from the remote layer.
That mean than any regular operation like rename, remove etc on
symlinks files always need to have their rclonelink suffix.
That way, we don't mess the internal map of items and avoid lots of
troubles.
When symlink support is disabled, Symlink and Readlink functions will
transparently manage ".rclonelink" files as regular files.
The tests are now run for the mount commands and for the plain VFS.
This makes the tests much easier to debug when running with a VFS than
through a mount.
