Add cpu usage to regression benchmarks (4th attempt)
Add cpu usage to regression benchmarks (4th attempt)

Summary:
Tested by running it on a remote machine.

I could not run it on the particular remote machine which has a different location for time command since it is busy and the script does not allow concurrent runs. So I tested it by hacking the script and replacing the command with "\$(hostname)" and confirmed that the scripts prints out the host name of the remote machine.
Closes https://github.com/facebook/rocksdb/pull/2181

Differential Revision: D4921654

Pulled By: maysamyabandeh

fbshipit-source-id: 8abb5ea9f7234f3c50a749576ccbb47ff605beb9

vmx/rocksdb,SunguckLee/RocksDB,bbiao/rocksdb,SunguckLee/RocksDB,SunguckLee/RocksDB,SunguckLee/RocksDB,Andymic/rocksdb,Andymic/rocksdb,vmx/rocksdb,Andymic/rocksdb,SunguckLee/RocksDB,SunguckLee/RocksDB,Andymic/rocksdb,vmx/rocksdb,Andymic/rocksdb,Andymic/rocksdb,bbiao/rocksdb,bbiao/rocksdb,bbiao/rocksdb,vmx/rocksdb,SunguckLee/RocksDB,vmx/rocksdb,bbiao/rocksdb,Andymic/rocksdb,SunguckLee/RocksDB,bbiao/rocksdb,vmx/rocksdb,vmx/rocksdb,bbiao/rocksdb,vmx/rocksdb,bbiao/rocksdb,Andymic/rocksdb