block-migration: improve "Unknown flags" error message

Show the actual flags value and include "block migration" in the error
message so it's clear where the error is coming from.
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>
Message-id: 1360534366-26723-2-git-send-email-stefanha@redhat.com
Signed-off-by: NAnthony Liguori <aliguori@us.ibm.com>

block-migration.c

@@ -695,7 +695,7 @@ static int block_load(QEMUFile *f, void *opaque, int version_id)
                    (addr == 100) ? '\n' : '\r');
             fflush(stdout);
         } else if (!(flags & BLK_MIG_FLAG_EOS)) {
-            fprintf(stderr, "Unknown flags\n");
+            fprintf(stderr, "Unknown block migration flags: %#x\n", flags);
             return -EINVAL;
         }
         ret = qemu_file_get_error(f);