tlsdated.conf: make sure the permissions are updated

/var/cache/tlsdated/timestamp was 0600 but now it should
be 0644.  Newly created files are properly permissioned
but existing files are not changed and are unreadable by
tlsdated during startup.

This change ensures the permissions are correct.

TEST=(in progress) emerge on to x86-alex, chmod 0600 /var/cache/tlsdated/timestamp, initctl restart tlsdated, ls -la /var/cache/tlsdated
BUG=chromium:315905

Change-Id: Iba513635c7ba7dd23f2645e56852959ab27aeaf4
Reviewed-on: https://chromium-review.googlesource.com/175905
Reviewed-by: Kees Cook <keescook@chromium.org>
Tested-by: Will Drewry <wad@chromium.org>
Commit-Queue: Will Drewry <wad@chromium.org>
Reviewed-by: Will Drewry <wad@chromium.org>
(cherry picked from commit a6d30dbfe6d4e7173961fcc0f9abcf8701c89ce9)
Reviewed-on: https://chromium-review.googlesource.com/176121
1 file changed