dri2: reply to client for WaitMSC request in any case

otherwise client would wait for reply forever and desktop appears hang.

Signed-off-by: Flora Cui <flora.cui@amd.com>
Acked-by: Feifei Xu <Feifei.Xu@amd.com>
Reviewed-by: Michel Dänzer <michel.daenzer@amd.com>
12 jobs for master in 1 minute and 4 seconds (queued for 2 seconds)
latest
Status Job ID Name Coverage
  Docker Image
passed #348119
debian-testing

00:00:16

 
  Build
passed #348122
xserver-1.13

00:00:42

passed #348123
xserver-1.14

00:00:28

passed #348124
xserver-1.15

00:00:28

passed #348125
xserver-1.16

00:00:46

passed #348126
xserver-1.17

00:00:47

passed #348127
xserver-1.18

00:00:46

passed #348128
xserver-1.18-clang

00:00:36

passed #348129
xserver-1.19

00:00:46

passed #348130
xserver-1.19-clang

00:00:36

passed #348120
xserver-1.20

00:00:42

passed #348121
xserver-1.20-clang

00:00:38