Summary: This will make it easier for admins and devs to use RepairDB.
Test Plan:
Tried deleting the manifest and verified it recovers:
$ ldb --create_if_missing --db=/tmp/test_db put ok ok
$ rm -f /tmp/test_db/MANIFEST-000001
$ ./ldb --db=/tmp/test_db repair
$ ldb --db=/tmp/test_db get ok
ok
Reviewers: yhchiang, sdong, IslamAbdelRahman
Reviewed By: IslamAbdelRahman
Subscribers: leveldb, andrewkr, dhruba
Differential Revision: https://reviews.facebook.net/D55359
08304c0867