msvideo1enc: fix initial keyframe value

keyframe was never set to anything but 1

Fixes CID733730
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/msvideo1enc.c

@@ -71,7 +71,7 @@ static int encode_frame(AVCodecContext *avctx, AVPacket *pkt,
     uint16_t *src;
     uint8_t *prevptr;
     uint8_t *dst, *buf;
-    int keyframe = 1;
+    int keyframe = 0;
     int no_skips = 1;
     int i, j, k, x, y, ret;
     int skips = 0;

tests/ref/fate/vsynth1-msvideo1

-37aa67b5928794534cb6a268d4adf48c *tests/data/fate/vsynth1-msvideo1.avi
+afe516f762a598f3f9c7ae8a9f288d3e *tests/data/fate/vsynth1-msvideo1.avi
 2162264 tests/data/fate/vsynth1-msvideo1.avi
-c0665fac1bd896b6fe7fe0eead805bd5 *tests/data/fate/vsynth1-msvideo1.out.rawvideo
+ef76473f7be587dac7676a69835e43ce *tests/data/fate/vsynth1-msvideo1.out.rawvideo
 stddev:   11.80 PSNR: 26.69 MAXDIFF:  151 bytes:  7603200/  7603200