sstate-cache-management.sh: fix it for downloaded file
Fix it for the downloaded sstate cache file
* The downloaded sstate cache file is in SSTATE_DIR, and there is a
symlink points to it, the sstate cache file should not be removed if
the corresponding symlink is kept, it would be removed when the
symlink is removed (with -L option).
* Fix a comment line.
[YOCTO #2897]
Signed-off-by: Robert Yang <liezhi.yang@windriver.com> Signed-off-by: Saul Wold <sgw@linux.intel.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
