[RocksDB] add back --mmap_read options to crashtest

Summary: As title, now that db_stress supports --map_read properly

Test Plan: make crash_test

Reviewers: vamsi, emayanke, dhruba

CC: leveldb

Differential Revision: https://reviews.facebook.net/D11391

tools/db_crashtest.py

@@ -66,6 +66,7 @@ def main(argv):
         run_had_errors = False
         additional_opts = ' --disable_seek_compaction=' + \
                           str(random.randint(0, 1)) + \
+                          ' --mmap_read=' + str(random.randint(0, 1)) + \
                           ' --block_size=16384 ' + \
                           ' --cache_size=1048576 ' + \
                           ' --open_files=500000 ' + \

tools/db_crashtest2.py

@@ -71,6 +71,7 @@ def main(argv):
         run_had_errors = False
         additional_opts = ' --disable_seek_compaction=' + \
                           str(random.randint(0, 1)) + \
+                          ' --mmap_read=' + str(random.randint(0, 1)) + \
                           ' --block_size=16384 ' + \
                           ' --cache_size=1048576 ' + \
                           ' --open_files=500000 ' + \