format: Restore upstream version before bump check

Since we build +20 before +10, when finishing the +10 build the upstream
points to the old upstream version. This means that fetching the format
will get +10 format instead of the +20 format which will make
checkBumpNeeded() erroneously return true.
This patch fix a crash where format bump would loop forever until it hit
a format beyond the last existing one and crash.

Signed-off-by: Rodrigo Chiossi <rodrigo.chiossi@intel.com>

mixer/cmd/build.go

@@ -156,6 +156,8 @@ var buildUpstreamFormatCmd = &cobra.Command{
 			if err = b.UnstageMixFromBump(); err != nil {
 				fail(err)
 			}
+			b.UpstreamVerUint32 += 10
+			b.UpstreamVer = strconv.FormatUint(uint64(b.UpstreamVerUint32), 10)
 			bumpNeeded, err = b.CheckBumpNeeded(silent)
 			if err != nil {
 				fail(err)