msdkvpp: don't use NV12 as default output in normal mode

If so, BGRA is the preferred output format hence BGRA will be selected
as input format by default, e.g. in the pipleline below, BGRA instead of
NV12 is selected without renegotiation, so we can avoid the NV12 issue
(see commit 3f2314a1) by default.

gst-launch-1.0 videotestsrc ! msdkvpp ! glimagesink
6 jobs for fix-msdkvpp in 24 minutes and 14 seconds (queued for 1 second)
Status Job ID Name Coverage
  Preparation
passed #75264
gst indent

00:00:28

passed #75263
manifest

00:00:19

 
  Build
passed #75265
build fedora x86_64

00:02:09

 
  Test
passed #75266
check fedora

00:15:27

 
  Full Builds
passed #75267
build android arm64 api28

00:03:46

passed #75268
build cerbero fedora x86_64

00:06:08