wined3d: Pass GL_SYNC_FLUSH_COMMANDS_BIT to glClientWaitSync() if WINED3DGETDATA_FLUSH was specified.

Otherwise the application may keep spinning on wined3d_query_get_data() in
case the query wasn't submitted to the GPU yet when wined3d_query_get_data()
was called. This issue was exposed by commit
70889d68. Note that this won't fix the issue
if the query was created in a different GL context.
Signed-off-by: Henri Verbeet <hverbeet@codeweavers.com>
Signed-off-by: Alexandre Julliard <julliard@winehq.org>