block: Remove error messages in bdrv_make_zero()

There is only a single caller of bdrv_make_zero(), which is qemu-img
convert. If the function fails, we just fall back to a different method
of zeroing out blocks on the target image. There is no good reason to
print error messages on stderr when the higher level operation will
actually succeed.
Signed-off-by: NKevin Wolf <kwolf@redhat.com>
Acked-by: NEric Blake <eblake@redhat.com>

block/io.c

@@ -909,8 +909,6 @@ int bdrv_make_zero(BdrvChild *child, BdrvRequestFlags flags)
         }
         ret = bdrv_block_status(bs, offset, bytes, &bytes, NULL, NULL);
         if (ret < 0) {
-            error_report("error getting block status at offset %" PRId64 ": %s",
-                         offset, strerror(-ret));
             return ret;
         }
         if (ret & BDRV_BLOCK_ZERO) {
@@ -919,8 +917,6 @@ int bdrv_make_zero(BdrvChild *child, BdrvRequestFlags flags)
         }
         ret = bdrv_pwrite_zeroes(child, offset, bytes, flags);
         if (ret < 0) {
-            error_report("error writing zeroes at offset %" PRId64 ": %s",
-                         offset, strerror(-ret));
             return ret;
         }
         offset += bytes;