12364 mdb trips assertion related to autowrap

@@ -19,11 +19,11 @@
  * CDDL HEADER END
  */
 /*
  * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
  * Use is subject to license terms.
- * Copyright 2019 Joyent, Inc.
+ * Copyright 2020 Joyent, Inc.
  * Copyright (c) 2017 by Delphix. All rights reserved.
  */
 
 /*
  * Format String Decoder

@@ -731,11 +731,11 @@
         if (!(fp->f_type & FMT_NOAUTOWRAP)) {
                 /*
                  * Unless a format has explicitly opted out, we force autowrap
                  * for the duration of mdb_fmt_print().
                  */
-                mdb.m_flags |= MDB_FL_AUTOWRAP;
+                mdb_iob_set_autowrap(mdb.m_out);
         }
 
         switch (FMT_TYPE(fp->f_type)) {
         case FMT_FUNC:
                 funcp = (mdb_fmt_func_f *)fp->f_ptr;