Fix crash_test

Summary:
crash_test grep for 'fail' string in the output and if found it consider that we failed.
Update the output to use something else

Test Plan: make crash_test (still running)

Reviewers: yhchiang, sdong, andrewkr

Reviewed By: andrewkr

Subscribers: andrewkr, dhruba

Differential Revision: https://reviews.facebook.net/D57381

tools/db_stress.cc

@@ -643,7 +643,7 @@ class Stats {
     fprintf(stdout, "%-12s: Got errors %ld times\n", "", errors_);
     fprintf(stdout, "%-12s: %ld CompactFiles() succeed\n", "",
             num_compact_files_succeed_);
-    fprintf(stdout, "%-12s: %ld CompactFiles() failed\n", "",
+    fprintf(stdout, "%-12s: %ld CompactFiles() did not succeed\n", "",
             num_compact_files_failed_);
 
     if (FLAGS_histogram) {