Summary:
copied from: https://github.com/mdlugajczyk/rocksdb/commit/5ebfd2623a01e69a4cbeae3ed2b788f2a84056ad

Opening existing RocksDB attempts recovery from log files, which uses
wrong sequence number to create the memtable. This is a regression
introduced in change a4003363.

This change includes a test demonstrating the problem, without the fix
the test fails with "Operation failed. Try again.: Transaction could not
check for conflicts for operation at SequenceNumber 1 as the MemTable
only contains changes newer than SequenceNumber 2.  Increasing the value
of the max_write_buffer_number_to_maintain option could reduce the
frequency of this error"

This change is a joint effort by Peter 'Stig' Edwards thatsafunnyname
and me.
Closes https://github.com/facebook/rocksdb/pull/1458

Differential Revision: D4143791

Pulled By: reidHoruff

fbshipit-source-id: 5a25033