vm: O_TRUNC is meaningless when creating a file with O_EXCL

slapos/recipe/vm.py

@@ -199,7 +199,7 @@ class InstallDebianRecipe(BaseRecipe):
       for dist, iso, kernel, initrd in self.dists:
         vm = join(location, dist + '.img')
         args = self.getQemuBasicArgs(dist, 256, unsafe=True)
-        open_flags = os.O_CREAT | os.O_EXCL | os.O_WRONLY | os.O_TRUNC
+        open_flags = os.O_CREAT | os.O_EXCL | os.O_WRONLY
         fd = os.open(vm, open_flags, 0666)
         try:
           os.ftruncate(fd, self.size)