Do not use warning_pre_print in linux-thread-db.c

linux-thread-db.c may print "warning_pre_print" before displaying an
error message.  This seems like a mistake to me, and furthermore I
think it's best to be as sparing as possible with uses of
warning_pre_print, so this patch removes the prefix.

Reviewed-By: Keith Seitz <keiths@redhat.com>



diff --git a/gdb/linux-thread-db.c b/gdb/linux-thread-db.c
index 9d84187..f946c2a 100644
--- a/gdb/linux-thread-db.c
+++ b/gdb/linux-thread-db.c
@@ -778,9 +778,6 @@ check_thread_db (struct thread_db_info *info, bool log_progress)
     }
   catch (const gdb_exception_error &except)
     {
-      if (warning_pre_print)
-	gdb_puts (warning_pre_print, gdb_stderr);
-
       exception_fprintf (gdb_stderr, except,
 			 _("libthread_db integrity checks failed: "));