osd: erasure code benchmark tool

osd: erasure code benchmark tool

Implement the ceph_erasure_code_benchmark utility to:

* load an erasure code plugin

* loop over the encode/decode function using the parameters from the
  command line

* print the number of bytes encoded/decoded and the time to process

When decoding, random chunks ( as set with --erasures ) are lost on each
run.

For instance:

    $ ceph_erasure_code_benchmark \
       --plugin jerasure \
       --parameter erasure-code-directory=.libs \
       --parameter erasure-code-technique=reed_sol_van \
       --parameter erasure-code-k=2 \
       --parameter erasure-code-m=2 \
       --workload decode \
       --erasures 2 \
       --iterations 1000
    0.964759	1048576

shows 1GB is decoded in 1second.

It is intended to be used by other scripts to present a human readable
output or detect performance regressions.

Signed-off-by: Loic Dachary <loic@dachary.org>