Dedup code in option.cc and db_options.cc
Dedup code in option.cc and db_options.cc

Summary:
The code in DBOptions::Dump is simply a duplicate of the code in ImmutableDBOptions::Dump and MutableDBOptions.Dump

consolidate duplicate code.

tested visually
Closes https://github.com/facebook/rocksdb/pull/1818

Differential Revision: D4486710

Pulled By: IslamAbdelRahman

fbshipit-source-id: 7085189

Andymic/rocksdb,SunguckLee/RocksDB,SunguckLee/RocksDB,SunguckLee/RocksDB,SunguckLee/RocksDB,Andymic/rocksdb,Andymic/rocksdb,vmx/rocksdb,vmx/rocksdb,Andymic/rocksdb,SunguckLee/RocksDB,SunguckLee/RocksDB,bbiao/rocksdb,bbiao/rocksdb,bbiao/rocksdb,vmx/rocksdb,bbiao/rocksdb,Andymic/rocksdb,bbiao/rocksdb,vmx/rocksdb,vmx/rocksdb,wat-ze-hex/rocksdb,vmx/rocksdb,Andymic/rocksdb,vmx/rocksdb,SunguckLee/RocksDB,wat-ze-hex/rocksdb,wat-ze-hex/rocksdb,wat-ze-hex/rocksdb,bbiao/rocksdb,bbiao/rocksdb,wat-ze-hex/rocksdb,vmx/rocksdb,bbiao/rocksdb,Andymic/rocksdb,Andymic/rocksdb,wat-ze-hex/rocksdb,SunguckLee/RocksDB,wat-ze-hex/rocksdb,wat-ze-hex/rocksdb