RFC - d3d9: Return success for UnlockRect attempts on already unlocked surfaces

[Bruno Jesus]

Hi all, this is an attempt to fix bug 28874 [1]. The tests [2] run
fine up to Windows 8, which unfortunately introduced a change in the
behavior so I'm not sure how to handle this (broken?).

Maybe a similar test is required in other d3d versions and a deeper
change (wined3d_surface_unmap?) required to proper fix this.

[1] - https://bugs.winehq.org/show_bug.cgi?id=28874
[2] - https://testbot.winehq.org/JobDetails.pl?Key=17252

Best wishes,
Bruno