[RI1][RC1] Add ceph bench and rbd bench into Functest

[collivier]

Ceph-bench and rbd bench can enhance disk benchmarking testing
https://tracker.ceph.com/projects/ceph/wiki/Benchmark_Ceph_Cluster_Performance

[collivier]

@acmacm @rabi-abdel @fuqiao123 @scottsteinbrueck let me know if one new contributor can help here (not so difficult).

[jayacha]

Waiting for volunteers

[jayacha]

@collivier requesting to add additional swift tests for additional coverage of the requirements to improve the test coverage (related to RA1 ch5 section5.2.4 swift). this issues not related to Airship 39/40/41.

[chetanchib]

rbd bench - ceph performance tool templates with results for sample pool/image mapped, on storage cluster with ceph version 12.2.12-101.el7cp luminous (stable):

rbd -p <pool_name> bench <image_name> –io-type <read | write> [–io-size size-in-B/K/M/G/T] [–io-threads num-ios-in-flight] [–io-total size-in-B/K/M/G/T] [–io-pattern <seq | rand>]

rbd bench- ceph performance tool.pdf

[Vaib16dec]

rbdbench is handled in this https://gerrit.opnfv.org/gerrit/c/functest/+/71242
If needed, we can separate two issues, rbdbench and cephbench.